Ketones for runners: what's being used and what the research says
We report what runners are using and what the research says. We don't recommend taking any supplement. Talk to your GP or a registered sports dietitian before trying one.
Quick answer
Research suggests they don't. Two meta-analyses of randomised trials found no effect on endurance performance[1][2], and a review of studies in endurance runners found no benefit[3]. Trials over 5 km and 10 km found no difference[4][5]. Taking ketones after training is a newer idea, with mixed results so far[6][7].
- Research
- Weak (proposed)Meta-analyses found no performance benefit, and running trials from 5 km to 10 km found none. Stomach upset is common.
- Proposed by our editor; not yet confirmed by an expert reviewer.
- WADA status
- Permitted
- Distances in the research
- 800 m–5K: studied10K–half: limited researchMarathon: not studiedUltra: limited research
What are ketone supplements?
Ketone bodies (beta-hydroxybutyrate, acetoacetate and acetone) are made by the liver when energy or carbohydrate is short, such as during prolonged fasting or a low-carbohydrate diet[8]. Beta-hydroxybutyrate (BHB) is the one usually measured. Ketone supplements raise blood ketones without cutting carbohydrate, and can lift blood BHB above 2 mM soon after a drink[8].
They come in several forms[8]. Ketone esters, such as the monoester (R)-3-hydroxybutyl (R)-3-hydroxybutyrate, are salt-free and raise D-BHB, the form the body mainly uses, quickly and in line with the dose. Ketone salts are usually a mix of D- and L-BHB bound to calcium, sodium or potassium. 1,3-butanediol is a precursor that the body turns into BHB[8].
The forms differ a lot in what they do to blood levels. In healthy volunteers, a ketone ester drink raised blood D-BHB to a peak of 2.8 mM, against 1.0 mM for ketone salts[9]. Half the BHB in the salt drinks was the L form, which stayed raised for more than 8 hours, and eating a meal before a ketone ester cut the peak by a third[9]. In a meta-analysis, monoesters appeared to raise blood ketones more than precursors[2], and the AIS says salts appear extremely unlikely to raise blood BHB enough, meaning above 1 mmol/L[8].
The Australian Institute of Sport (AIS) lists ketone supplements in Group B, for use in research or clinical monitoring, and notes that ketone esters are expensive and often hard to get[8].
Also called: ketone esters, ketone salts, ketone drinks, exogenous ketones, beta-hydroxybutyrate (BHB).
Why are ketone supplements getting attention?
Ketone supplements have become popular with endurance runners on the promise of delaying fatigue[3]. We found no survey measuring how many runners use them.
Interest grew after an early cycling study found about 2% more distance in a 30-minute time trial, a benefit most later studies haven't supported[10][11]. That 2016 paper reported five studies in 39 high-performance athletes, in which ketosis lowered muscle glycolysis and blood lactate and raised the burning of fat stored in muscle[12]. Use in professional cycling is reportedly still widespread[10], and the AIS notes media criticism of cycling teams over a lack of openness about how and why they used ketones[8].
The AIS says performance has been tested in more than 50 studies, with no scientific consensus on a benefit[8]. More recently, research has shifted from taking ketones before exercise to taking them after it, to help recovery and adaptation to training[13].
The claims, checked against the research
Faster race timesNot supported
Two meta-analyses of randomised trials found no effect on endurance performance[1][2]. Running trials over 5 km and 10 km found no difference[14][5], and a ketone diester made professional cyclists about 2% slower over 31 km[15].
An extra fuel that spares glycogenNot supported
The AIS says recent studies suggest ketones supply only about 2 to 5% of the fuel used during exercise[8]. In 12 highly trained cyclists, a ketone ester early in a 3-hour simulated race didn't spare muscle glycogen[16].
Better running economyMixed
In 11 male runners, a ketone monoester taken without carbohydrate improved running economy by 4.1% compared with a carbohydrate drink, but not when taken with carbohydrate[17]. In 18 trained runners, the same comparison found no change in running economy, while advanced running shoes did improve it[18]. In 8 runners, running economy during an hour's run before a 10 km time trial was also similar with and without a ketone ester[5].
Recovering faster between hard sessionsMixed
In a 3-week overload study, 18 fit men who drank a ketone ester after each session sustained a 15% higher training load in week 3 and showed fewer signs of overreaching[19]. But an 8-day simulated cycling race found no clear benefit for recovery[7], and ketones didn't speed the recovery of muscle strength after muscle-damaging exercise[20].
Bigger gains from trainingMixed
In 28 trained men, a ketone ester after training and before sleep for 8 weeks led to 4% higher 30-minute time-trial power than placebo[6]. That is one trial in male cyclists, and the positive findings on taking ketones after exercise that we found come mainly from one research group[13][19].
Faster glycogen refuellingMixed
With glucose infused into a vein to keep blood glucose high, a ketone ester left muscle glycogen 50% higher than a control drink in 12 athletes[21], but added to a normal recovery drink it made no difference in 8 trained men[22]. In runners, a ketone ester increased the carbohydrate retained during a 4-hour recovery but didn't change a second run to exhaustion[23].
A sharper mind late in a raceMixed
In a 100 km trail run, runners given a ketone ester kept their reaction times, while the placebo group's slowed[24], and 31 days of a ketone ester sped responses on two cognitive tests in recreational runners[4]. A ketone ester also limited errors in a multitasking test after shuttle running[25], but cognitive tests showed no benefit around a 10 km time trial[5] or in an 8-day simulated cycling race[7].
Better sleep after hard trainingMixed
In 10 well-trained cyclists, a ketone ester after evening exercise and before bed improved sleep efficiency by 3%[26]. In an 8-day simulated cycling race, it had no effect on sleep[7].
How do ketone supplements work?
The original idea was an extra fuel for muscles and the brain[8]. But recent studies suggest ketones supply only about 2 to 5% of the fuel used during exercise[8]. In 6 athletes, the share of energy from burning a ketone ester peaked at about 4.5%, and doubling blood BHB from about 2 to 4.4 mM didn't raise it[27].
Ketone esters also make the blood more acidic. A ketone ester drink lowered blood pH by 0.10 at rest[9], and during a simulated cycling race pH fell from about 7.42 to 7.36 and bicarbonate from 26.0 to 21.6 mM[16]. The AIS says this acidosis may work against performance in some sports[8].
Ketone drinks lower blood glucose. At rest, ketone drinks lowered blood glucose, fatty acids and triglycerides[9], and during recovery from running, a ketone ester kept blood glucose more than 1 mmol/L lower[23]. When glucose was infused to keep it high, a ketone ester doubled insulin levels[21].
The newer idea is that ketones taken after exercise may help recovery and adaptation, with reported effects on sleep, overtraining symptoms, blood-vessel growth in muscle and the hormone erythropoietin (EPO)[13]. The AIS says more work is needed to find out whether the rise in EPO leads to changes in haemoglobin that would matter for sport[8].
Do ketone supplements improve running performance?
No. Two meta-analyses of randomised trials found no effect on endurance performance, one covering ketone esters and salts[1], the other esters and related precursors[2]. A review of 12 studies in endurance runners found no benefit from ketone supplements or ketogenic diets[3]. A newer line of research, taking ketones after training, has produced one positive 8-week trial in male cyclists[6] and one 8-day trial that found no clear benefit[7].
800 m to 5K (Studied)
Over 5 km, trials found no difference with a ketone precursor taken with carbohydrate[28], with ketone salts plus MCT oil taken an hour before a treadmill time trial[14], or after 31 days of a ketone ester[4].
In an 800 m trial in 32 endurance-trained men and women, 10 days of ketone salts didn't change a first run, though the ketone group's average over two runs got faster[29]. In 18 middle- and long-distance runners, a ketone ester didn't improve running economy or time to exhaustion compared with carbohydrate[18].
10K to half marathon (Limited research)
In 8 trained runners, a ketone ester with carbohydrate made no difference to a 10 km time trial after an hour of running: 2,402 seconds against 2,422 with carbohydrate alone[5]. Elite race walkers who took a ketone ester after a 5-day ketogenic diet were about 6% slower over 10,000 m[30].
For context, elite race walkers who spent 3 weeks on a ketogenic diet didn't improve their 10 km times, while those eating high or periodised carbohydrate improved by 5 to 7%[31]. We found no trials of ketone supplements over a half marathon.
Marathon (Not studied)
We found no controlled trials of ketone supplements in marathons. The largest meta-analysis covered events of up to about 50 minutes[1].
The closest evidence comes from cycling. In a 3-hour simulated race with carbohydrate, a ketone ester neither spared glycogen nor improved the final 15-minute time trial[16]. In WorldTour cyclists, blood BHB was back near baseline after 4.5 hours of riding[32].
Ultra (Limited research)
In a 100 km trail run, 18 male recreational runners took a ketone ester or placebo before, during and after; 8 finished the full distance, while 6 stopped at 80 km and 4 at 60 km[24][3]. Blood BHB stayed at about 2 to 3 mM with the ester, and those runners kept their reaction times while the placebo group's slowed[24].
A review of runner studies reports that the ketone ester made no difference to performance in that trial[3]. The ISSN says evidence for ketones in ultra-marathons is lacking[11].
Study by study
| Study | Who took part | What they took | What was measured | What they found |
|---|---|---|---|---|
| Valenzuela 2020 [1]Meta-analysis | 13 randomised trials | Single doses of ketone esters or salts v drinks without ketones | Exercise performance, from sprints to events of about 50 minutes | No effect overall, on time trials, or for esters or salts separately |
| Brooks 2022 [2]Meta-analysis | 8 randomised trials, 80 people (77 men) | Single doses of ketone monoesters or precursors v control drinks | Endurance performance: time trials and time to exhaustion | No significant effect. 6 of 7 studies that checked found more gut symptoms with ketones |
| Sun 2025 [3]Systematic review | 12 studies, 132 endurance runners (131 men) | 7 studies of ketone supplements and 5 of ketogenic diets | VO2max, race times, time to exhaustion | None found a benefit for aerobic performance |
| Leckey 2017 [15]Randomised controlled trial | 10 elite male professional cyclists (randomised crossover) | Ketone diester, 2 doses of 250 mg per kg, in the 30 minutes before a warm-up | About 31 km laboratory time trial | About 2% slower than placebo, with gut discomfort and higher perceived effort |
| Prins 2020 [14]Randomised controlled trial | 10 recreational runners (randomised crossover) | 300 mg per kg of BHB salts plus MCT oil, 60 minutes before | Treadmill 5 km time trial | No significant difference: 1,430 v 1,488 seconds with placebo |
| Scott 2019 [28]Randomised controlled trial | 11 male runners (randomised crossover) | 1,3-butanediol with carbohydrate v an energy-matched carbohydrate drink | 5 km time trial after 60 minutes of running | No difference: 1,261 v 1,265 seconds |
| Evans 2019 [5]Randomised controlled trial | 8 endurance-trained runners (randomised crossover) | 573 mg per kg of ketone monoester with an 8% carbohydrate drink, before and during | 10 km treadmill time trial after 1 hour of running | No difference: 2,402 v 2,422 seconds with carbohydrate alone |
| Prins 2026 [4]Randomised controlled trial | 18 recreational runners (single-blind randomised trial) | 30 g of ketone monoester or placebo, three times a day for 31 days | 5 km time trial, cognitive tests, mood | 5 km performance unchanged. Faster responses on two cognitive tests |
| Brady 2025 [18]Randomised controlled trial | 18 middle- and long-distance runners, 8 of them women (randomised crossover) | 500 mg per kg of ketone monoester 20 minutes before and 250 mg per kg during, v carbohydrate | Running economy and time to exhaustion, in two types of shoe | Ketone ester didn't change running economy. Advanced shoes did |
| Whitfield 2021 [30]Non-randomised trial | 18 elite race walkers, 15 men and 3 women (groups not randomised) | 5-day ketogenic diet plus 573 mg per kg of ketone ester, v high-carbohydrate diet | Real 10,000 m race | About 6% slower in the ketogenic-diet group; unchanged with high carbohydrate |
| Poffé 2023 [24]Randomised controlled trial | 18 male recreational ultrarunners (double-blind, randomised) | Ketone ester 25 g before, 25 g an hour during and 5 doses of 25 g over 24 hours after, v placebo | 100 km trail run (8 finished), reaction times, muscle biopsies | Reaction times held with ketones and slowed with placebo. A later review reports no performance difference |
| Poffé 2021 [33]Randomised controlled trial | 9 well-trained male cyclists (randomised crossover) | 65 g of ketone ester, bicarbonate, both, or control, with 60 g of carbohydrate an hour | 15-minute time trial and sprint after 3 hours of riding | Time-trial power 5% higher only with ketone ester plus bicarbonate; ester alone no different |
| Poffé 2019 [19]Randomised controlled trial | 18 fit men (randomised) | Ketone ester or control drink after each session, 3 weeks of twice-daily training | Training load, heart rate, 2-hour ride | 15% higher training load in week 3 and fewer signs of overreaching |
| Robberechts 2026 [6]Randomised controlled trial | 28 trained men, 14 per group (randomised, placebo-controlled) | 25 g of ketone monoester or placebo after exercise and before sleep, 8 weeks of cycling training | 30-minute time trial, VO2peak, muscle biopsies | Time-trial power 4% higher than placebo (302 v 291 W) |
| Clarke 2025 [23]Randomised controlled trial | 13 endurance-trained men aged 18 to 61 (randomised crossover) | Ketone monoester 0.29 g per kg an hour, with sucrose and whey, during 4 hours' recovery | Second run to exhaustion; carbohydrate storage | More carbohydrate retained, but no difference in the second run: 52 v 54 minutes |
The key studies, in order
- 2016TrialFive studies in 39 high-performance athletes: ketosis from a ketone ester drink lowered muscle glycolysis and blood lactate, and raised fat burning. [12]
- 2017Non-randomised trialElite race walkers: after 3 weeks of intensified training, carbohydrate diets improved 10 km times by 5-7%; a ketogenic diet gave no gain and worse economy. [31]
- 2017Trial12 well-trained men, with glucose infused to hold blood glucose high: after a ketone ester drink, muscle glycogen was 50% higher than after control at the end of 2 hours' recovery. [21]
- 2017Trial10 professional cyclists: a ketone diester made a 31 km time trial about 2% slower. All reported gut discomfort, and an eleventh rider couldn't start because of vomiting. [15]
- 2017TrialHealthy volunteers: a ketone ester raised blood D-BHB to a peak of 2.8 mM, against 1.0 mM for ketone salts. A meal first cut the peak by a third. The ester lowered blood pH. [9]
- 2017Trial8 trained men: adding a ketone ester to a protein and carbohydrate recovery drink didn't change glycogen resynthesis over 5 hours. [22]
- 2018Trial11 male team-sport athletes: a ketone ester with carbohydrate didn't change shuttle-run time to exhaustion, but limited errors in a multitasking test afterwards. [25]
- 2018ConsensusSupplements can contain prohibited substances as undeclared ingredients or contaminants, and athletes are responsible for anything found in their sample. [41]
- 2019Trial8 endurance-trained runners: a ketone ester with carbohydrate made no difference to a 10 km time trial after an hour of running, compared with carbohydrate alone. [5]
- 2019Trial18 fit men, 3 weeks of twice-daily training: a ketone ester after each session gave a 15% higher sustainable training load in week 3 and blunted signs of overreaching. [19]
- 2019Trial11 male runners: a ketone precursor with carbohydrate made no difference to a 5 km time trial after 60 minutes of running, compared with carbohydrate alone. [28]
- 2019TrialThree studies of ketone drinks: gut symptoms were mostly mild and short-lived, and high-dose ketone salts caused the most. Authors linked to a ketone drink maker. [37]
- 2019ConsensusEvidence for ketogenic diets or ketone esters improving ultra-marathon performance is lacking; performance benefits of ketone esters have been repeatedly refuted. [11]
- 2020Systematic review10 trials, 112 people (109 men), 16 performance outcomes: 3 positive, 10 null and 3 negative. Results varied too much to conclude a benefit or harm. [35]
- 2020Trial12 highly trained male cyclists: a ketone ester early in a 3-hour simulated race didn't spare muscle glycogen or change the final time trial. Blood pH fell. [16]
- 2020Trial10 recreational runners: BHB salts plus MCT oil an hour before a treadmill 5 km time trial made no significant difference to finishing time. [14]
- 2020Meta-analysis13 randomised trials: no effect on exercise performance overall, on time trials, or for ketone esters or salts separately, in events of up to about 50 minutes. [1]
- 2021Trial6 athletes: the share of energy from burning a ketone ester peaked at about 4.5% during cycling, and doubling blood BHB didn't raise it. [27]
- 2021Trial9 well-trained male cyclists: after 3 hours of riding, 15-minute time-trial power was 5% higher only when a ketone ester was taken with bicarbonate. [33]
- 2021Trial14 well-trained male cyclists: a ketone ester lowered 30-minute time-trial power by 1.5%, even when bicarbonate offset the fall in blood pH. [42]
- 2021Non-randomised trial18 elite race walkers: after a 5-day ketogenic diet plus a ketone ester, all nine in that group raced 10,000 m about 6% slower. Walkers chose their diet group. [30]
- 2022Meta-analysis8 trials, 80 people (77 men): no effect on endurance performance. 6 of 7 studies that checked found more gut symptoms with ketones than with a control drink. [2]
- 2022Expert reviewAn early cycling study found about 2% more distance in a 30-minute time trial, but little support has followed despite many studies. Use in professional cycling is reportedly widespread. [10]
- 2022Trial16 healthy men and women: 27 g of ketone monoester three times a day for 3 days didn't speed recovery of muscle force after muscle-damaging exercise. [20]
- 2022Trial32 endurance-trained adults, 10 days of ketone salts: a first 800 m run didn't change; the ketone group's average over two runs got faster, the placebo group's didn't. [29]
- 2023Trial18 recreational runners on a 100 km trail run, 8 of whom finished: a ketone ester kept blood BHB at about 2-3 mM and prevented the slowing of reaction times seen with placebo. [24]
- 2023Trial10 well-trained cyclists: 25 g of ketone ester after evening exercise and before sleep improved sleep efficiency by 3% and countered the exercise-induced fall in REM sleep. [26]
- 2024Trial11 male runners: a ketone monoester without carbohydrate improved running economy by 4.1% compared with a carbohydrate drink, but not when taken with carbohydrate. Time to exhaustion didn't change. [17]
- 2024Trial28 male WorldTour cyclists, all also taking bicarbonate: a ketone ester raised mean power in an 8-minute time trial at the start of a simulated stage by 3.1% compared with placebo. [32]
- 2024Expert reviewNarrative review: ketones before or during exercise generally didn't improve performance; more studies report benefits when ketones are taken after exercise. [13]
- 2025Trial18 trained runners, 8 of them women: a ketone monoester didn't change running economy compared with a carbohydrate drink. Advanced running shoes improved it. [18]
- 2025Trial13 endurance-trained men, two runs to exhaustion 4 hours apart: a ketone ester in the recovery drinks raised carbohydrate stored but didn't change the second run. [23]
- 2025Systematic review12 studies, 132 endurance runners (131 men): none found that ketone supplements or ketogenic diets improved aerobic performance, including a 100 km ultra trial. [3]
- 2026Trial18 well-trained cyclists, 8-day simulated stage race: 25 g of ketone ester after each stage and before sleep gave no clear benefit for recovery, sleep, cognitive function or performance. [7]
- 2026Systematic review26 controlled studies from 2018 to 2025: ketones raised blood BHB and changed acid-base balance, but performance effects were mixed. Bicarbonate sometimes helped. [34]
- 2026Trial18 recreational runners: 30 g of a ketone ester three times a day for 31 days didn't change 5 km time-trial performance. [4]
- 2026Trial28 trained men, 8 weeks of cycling training: 25 g of ketone ester after exercise and before sleep gave 4% higher 30-minute time-trial power than placebo. [6]
Who has the research been done in?
Almost all of this research is in trained men, and many trials used cyclists rather than runners[2][3].
The athletes ranged from elite race walkers[30] and WorldTour cyclists[32] to recreational runners[14][4]. The only 100 km study used recreational runners[24], and one refuelling study included men aged 18 to 61[23]. The most positive recent findings, for taking ketones after training, come from trained male cyclists and fit men, not runners[6][19].
We found no trials in masters runners, teenagers or runners with medical conditions. A 2026 review limited to trained and physically active people found 26 controlled studies from 2018 to 2025, with mixed results[34].
What we know about women
Women are almost missing from this research: 1 of 132 runners in the runner review[3], 3 of 80 people in one meta-analysis[2] and 3 of 112 in a systematic review[35]. A few trials did include women: 16 of 32 endurance-trained adults in the 800 m trial[29], 8 of 18 in the running-economy trial[18], 3 of 18 elite race walkers[30], and 10 of 16 people in a muscle-damage study, which found no effect on strength recovery[20].
We found no studies of ketone supplements across the menstrual cycle, in pregnancy or while breastfeeding. The NHS pregnancy supplements page doesn't mention them, and says to speak to a GP about supplements beyond those it covers[36].
What the research can't tell us yet
Almost all participants were men: 131 of 132 runners in the runner review[3], and 77 of 80 people in one meta-analysis[2].
The trials were small, with 8 to 12 people each in one meta-analysis, and many used cycling rather than running[2]. Doses, timing, added carbohydrate or bicarbonate, and exercise tests all varied, which the AIS says makes a consensus hard to reach[8].
In the race-walking study, walkers chose their own diet group, and only the ketogenic-diet group took the ketone ester, so its effect couldn't be separated from the diet[30].
Many outcomes are markers, not performance. Rises in the hormone EPO and in muscle capillaries have been reported, but the AIS says it isn't known whether the EPO rise leads to changes in haemoglobin that matter for sport[8]. It also notes that in the 3-week overload study, the ketone group ate more energy and carbohydrate, which may have contributed to the fewer signs of overtraining[8].
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Research alerts
How and when are ketone supplements used in studies?
Studies in athletes used about 350 to 1,000 mg per kg of body mass (roughly 25 to 75 g), most often of a ketone ester taken before, and sometimes during, endurance exercise[8].
Running trials used, for example, 573 mg per kg of a ketone ester with carbohydrate around a 10 km time trial[5], or 30 g of a ketone ester three times a day for 31 days[4].
Studies of use after exercise mostly gave several doses of ketone monoester with a carbohydrate and protein recovery drink[8], typically 25 g after each session and again before sleep[6][7].
Some studies added sodium bicarbonate to offset the fall in blood pH: 65 g of ketone ester with 300 mg per kg of bicarbonate[33] or 800 mg per kg of ketone ester with 210 mg per kg of bicarbonate in WorldTour cyclists[32].
When studies gave it
Before-exercise studies gave the drink from about 20 to 60 minutes beforehand, sometimes with more during exercise[18][14][8]. Blood levels don't last: after a single ester drink, BHB was back to baseline within 3 to 4 hours[9], and in a 3-hour simulated race it was raised only in the first half[16].
After-exercise studies gave a dose straight after each session and another before sleep, over 8 days[7], 3 weeks[19] or 8 weeks[6]. The AIS says no consistent timing or dose has been established for this kind of use[8].
For recovery between two sessions on the same day, one running study gave a ketone ester in recovery drinks every 30 minutes across a 4-hour gap, with sucrose and whey protein[23]. The AIS advises that athletes first try ketone esters in training, before considering them for competition[8].
| What studies used | When | Ref. |
|---|---|---|
| About 350 to 1,000 mg per kg of body mass (25 to 75 g) | Most often before, and sometimes during, endurance exercise | [8] |
| 573 mg per kg of a ketone ester, with carbohydrate | Before and during an hour's run and a 10 km time trial | [5] |
| 300 mg per kg of ketone salts plus MCT oil | 60 minutes before a 5 km time trial | [14] |
| 30 g of a ketone ester, three times a day | 31 days, in recreational runners | [4] |
| 25 g of a ketone ester before, 25 g an hour during, five 25 g doses after | Around a 100 km trail run | [24] |
| 25 g of a ketone monoester | After each session and before sleep, for 8 weeks | [6] |
What are the side effects, and who should be careful?
Stomach upset is the main side effect: in one meta-analysis, 6 of 7 studies that checked found more gut symptoms with ketones than with a control drink[2]. All 10 professional cyclists who finished one trial reported gut discomfort, and one rider couldn't start because of vomiting[15].
The AIS says ketone salts carry a high salt load and are linked to severe gut side effects, and links both salts and 1,3-butanediol to nausea and gut upset[8]. A study by researchers linked to a ketone drink maker found symptoms were usually mild and short-lived[37].
Not every trial found more symptoms. With bicarbonate added, gut symptoms were similar across all conditions in one cycling study[33], and in a runner refuelling study, a ketone ester added only mild lower-gut symptoms during the second run[23].
Ketone esters also lower blood pH and bicarbonate: in one cycling study, pH fell from 7.43 to 7.36 and bicarbonate from 25.5 to 20.5 mM[33].
Medicines and health conditions
We found no NHS or MHRA guidance on ketone supplements themselves. The NHS describes diabetic ketoacidosis (DKA) as a serious condition in people with diabetes, where a lack of insulin causes ketones to build up in the blood[38]. For people with diabetes who test with a blood ketone meter, the NHS says under 0.6 mmol/L is normal and over 3 mmol/L is high[38]. Ketone drinks in studies raised blood BHB to about 2 to 3 mM in healthy people[9][4].
The MHRA says the diabetes medicines canagliflozin, dapagliflozin and empagliflozin (SGLT2 inhibitors) can rarely cause DKA, sometimes with only moderately raised blood glucose, and lists conditions leading to restricted food intake or severe dehydration among the risk factors[39]. Ketone drinks also lower blood glucose[9][23]. We found no studies of ketone supplements in people taking these medicines.
Be careful if
- You have a sensitive stomach: gut symptoms were more common with ketones in 6 of 7 studies that checked[2].
- You're planning to use them before a race: ketone drinks make the blood more acidic, which the AIS says may work against performance in some sports[8].
- You're also cutting carbohydrate: elite race walkers on a 5-day ketogenic diet plus a ketone ester were about 6% slower over 10,000 m[30].
- You have diabetes or take an SGLT2 inhibitor: the MHRA says these medicines can rarely cause diabetic ketoacidosis[39], and ketone drinks raise blood ketones and lower blood glucose[9].
- You're watching your salt intake: the AIS says ketone salts carry a high salt load[8].
Are ketone supplements allowed in competition?
The AIS says ketone esters are not on the World Anti-Doping Agency's Prohibited List[8]. WADA says its list is not exhaustive, so a substance not being named doesn't prove it is allowed[40].
Some sports bodies, such as the Movement for a Credible Cycling (MPCC), have advised members to avoid ketone supplements[8], and any supplement product can be contaminated with prohibited substances[41].
Independent quality-assurance schemes, often called batch testing, check supplement products for prohibited substances[41]. WADA says using a product from one of these schemes can reduce, but not eliminate, the risk of an anti-doping violation[40], and the IOC says no product can be guaranteed entirely safe[41].
Myth or evidence?
5 things runners hear about ketone supplements. Pick an answer to see what the research says.
1.Ketone drinks improve endurance performance.
2.During a run, ketones become a major fuel.
Show the answer
Myth. The AIS says recent studies suggest ketones supply only about 2 to 5% of the fuel used during exercise[8].
3.Ketone supplements can upset your stomach.
Show the answer
Evidence. Gut symptoms were more common with ketones in 6 of 7 studies that checked[2].
4.Ketone salts work as well as ketone esters.
Show the answer
Myth. The AIS says salts raise the form of ketone the body uses less than esters do[8].
5.Ketones are banned by WADA.
Show the answer
Myth. The AIS says ketone esters are not on the WADA Prohibited List[8].
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Frequently asked questions
- Do ketone drinks make you run faster?
- Research suggests not: two meta-analyses of randomised trials found no effect on endurance performance[1][2], and trials over 5 km and 10 km found no difference[28][5].
- What's the difference between ketone esters and ketone salts?
- The AIS describes esters as salt-free and generally well tolerated. Salts carry a high salt load, raise the form of ketone the body uses less, and are linked to severe gut side effects[8]. In one study, an ester drink raised blood D-BHB to 2.8 mM, against 1.0 mM for salts[9].
- Are ketone supplements banned in sport?
- The AIS says ketone esters aren't on the WADA Prohibited List[8], but WADA says its list isn't exhaustive[40], and some sports bodies, such as the Movement for a Credible Cycling (MPCC), have advised members to avoid them[8].
- Is taking ketones the same as a ketogenic diet?
- No. Supplements raise blood ketones without cutting carbohydrate, while a ketogenic diet does it by restricting carbohydrate[8]. A review in endurance runners found no performance benefit from either[3].
- Do ketone drinks upset the stomach?
- Often. In one meta-analysis, 6 of 7 studies that checked found more gut symptoms with ketones[2], and all 10 professional cyclists who finished one trial reported gut discomfort[15].
- Do ketones help recovery?
- The evidence is mixed. A ketone ester after each session blunted signs of overreaching in a 3-week overload study in fit men[19], but gave no clear recovery benefit in an 8-day simulated cycling race[7]. The AIS says effects on refuelling after exercise are conflicting[8].
- Do ketones help in an ultramarathon?
- The one trial we found showed no performance benefit. In a 100 km trail run, a ketone ester stopped reaction times slowing[24], but a later review reports no difference in performance[3], and the ISSN says evidence for ketones in ultra-marathons is lacking[11].
- Does taking bicarb with ketones help?
- Results are inconsistent. Bicarbonate with a ketone ester raised power by 5% in a time trial after 3 hours of cycling[33], but the same group then found a ketone ester lowered 30-minute time-trial power by 1.5%, even with bicarbonate[42].
- Do ketones help you refuel glycogen?
- The evidence is mixed. A ketone ester raised muscle glycogen when glucose was infused into a vein[21]; with a normal recovery drink it made no difference to glycogen[22], and in runners it increased the carbohydrate retained but didn't change a second run[23].
- Have ketone supplements been tested in women?
- Hardly. The runner review counted 1 woman among 132 runners[3]. Two running trials included more: 16 of 32 endurance-trained adults in an 800 m trial[29] and 8 of 18 in a running-economy trial[18].
References
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Meta-analysis13 randomised trials: no effect on exercise performance overall, on time trials, or for ketone esters or salts separately, in events of up to about 50 minutes.
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Brooks E, Lamothe G, Nagpal TS, et al. Acute ingestion of ketone monoesters and precursors do not enhance endurance exercise performance: a systematic review and meta-analysis. International Journal of Sport Nutrition and Exercise Metabolism, 2022.
Meta-analysis8 trials, 80 people (77 men): no effect on endurance performance. 6 of 7 studies that checked found more gut symptoms with ketones than with a control drink.
doi.org/10.1123/ijsnem.2021-0280 - [3]
Sun K, Choi YT, Yu CCW, et al. The effects of ketogenic diets and ketone supplements on the aerobic performance of endurance runners: a systematic review. Sports Health, 2025.
Systematic review12 studies, 132 endurance runners (131 men): none found that ketone supplements or ketogenic diets improved aerobic performance, including a 100 km ultra trial.
doi.org/10.1177/19417381241271547 - [4]
Prins PJ, Buga A, Storoschuk K, et al. The effects of 31-day exogenous ketone consumption on running performance, cognitive function, metabolism, body composition, hemodynamics, and mood in recreational runners: a randomized-control trial. Journal of the American Nutrition Association, 2026.
Randomised controlled trial18 recreational runners: 30 g of a ketone ester three times a day for 31 days didn't change 5 km time-trial performance.
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Evans M, McSwiney FT, Brady AJ, Egan B No benefit of ingestion of a ketone monoester supplement on 10-km running performance. Medicine and Science in Sports and Exercise, 2019.
Randomised controlled trial8 endurance-trained runners: a ketone ester with carbohydrate made no difference to a 10 km time trial after an hour of running, compared with carbohydrate alone.
doi.org/10.1249/MSS.0000000000002065 - [6]
Robberechts R, Bekhuis Y, Stalmans M, et al. Post-exercise ketone supplementation improves endurance performance and mitochondrial adaptations during an 8-week endurance training intervention. The Journal of Physiology, 2026.
Randomised controlled trial28 trained men, 8 weeks of cycling training: 25 g of ketone ester after exercise and before sleep gave 4% higher 30-minute time-trial power than placebo.
doi.org/10.1113/JP290315 - [7]
Engelbrecht L, Lauriks W, Robberechts R, et al. Ketone ester intake did not improve performance, neither cognitive function or sleep, during an 8-day simulated cycling race. Medicine and Science in Sports and Exercise, 2026.
Randomised controlled trial18 well-trained cyclists, 8-day simulated stage race: 25 g of ketone ester after each stage and before sleep gave no clear benefit for recovery, sleep, cognitive function or performance.
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Australian Institute of Sport AIS Sports Supplement Framework: Group B and linked fact sheets. Australian Sports Commission, 2026.
Consensus statementLists ketone supplements in Group B, for research or clinical monitoring. No scientific consensus on a performance benefit; recent studies suggest ketones supply only about 2-5% of fuel during exercise.
www.ausport.gov.au/ais/nutrition/supplements/group_b - [9]
Stubbs BJ, Cox PJ, Evans RD, et al. On the metabolism of exogenous ketones in humans. Frontiers in Physiology, 2017.
Randomised controlled trialHealthy volunteers: a ketone ester raised blood D-BHB to a peak of 2.8 mM, against 1.0 mM for ketone salts. A meal first cut the peak by a third. The ester lowered blood pH.
doi.org/10.3389/fphys.2017.00848 - [10]
Evans M, McClure TS, Koutnik AP, Egan B Exogenous ketone supplements in athletic contexts: past, present, and future. Sports Medicine, 2022.
Expert reviewAn early cycling study found about 2% more distance in a 30-minute time trial, but little support has followed despite many studies. Use in professional cycling is reportedly widespread.
doi.org/10.1007/s40279-022-01756-2 - [11]
Tiller NB, Roberts JD, Beasley L, et al. International Society of Sports Nutrition position stand: nutritional considerations for single-stage ultra-marathon training and racing. Journal of the International Society of Sports Nutrition, 2019.
Consensus statementEvidence for ketogenic diets or ketone esters improving ultra-marathon performance is lacking; performance benefits of ketone esters have been repeatedly refuted.
doi.org/10.1186/s12970-019-0312-9 - [12]
Cox PJ, Kirk T, Ashmore T, et al. Nutritional ketosis alters fuel preference and thereby endurance performance in athletes. Cell Metabolism, 2016.
Randomised controlled trialFive studies in 39 high-performance athletes: ketosis from a ketone ester drink lowered muscle glycolysis and blood lactate, and raised fat burning.
doi.org/10.1016/j.cmet.2016.07.010 - [13]
Robberechts R, Poffé C Defining ketone supplementation: the evolving evidence for postexercise ketone supplementation to improve recovery and adaptation to exercise. American Journal of Physiology - Cell Physiology, 2024.
Expert reviewNarrative review: ketones before or during exercise generally didn't improve performance; more studies report benefits when ketones are taken after exercise.
doi.org/10.1152/ajpcell.00485.2023 - [14]
Prins PJ, Koutnik AP, D'Agostino DP, et al. Effects of an exogenous ketone supplement on five-kilometer running performance. Journal of Human Kinetics, 2020.
Randomised controlled trial10 recreational runners: BHB salts plus MCT oil an hour before a treadmill 5 km time trial made no significant difference to finishing time.
doi.org/10.2478/hukin-2019-0114 - [15]
Leckey JJ, Ross ML, Quod M, et al. Ketone diester ingestion impairs time-trial performance in professional cyclists. Frontiers in Physiology, 2017.
Randomised controlled trial10 professional cyclists: a ketone diester made a 31 km time trial about 2% slower. All reported gut discomfort, and an eleventh rider couldn't start because of vomiting.
doi.org/10.3389/fphys.2017.00806 - [16]
Poffé C, Ramaekers M, Bogaerts S, Hespel P Exogenous ketosis impacts neither performance nor muscle glycogen breakdown in prolonged endurance exercise. Journal of Applied Physiology, 2020.
Randomised controlled trial12 highly trained male cyclists: a ketone ester early in a 3-hour simulated race didn't spare muscle glycogen or change the final time trial. Blood pH fell.
doi.org/10.1152/japplphysiol.00092.2020 - [17]
Brady AJ, Egan B Acute ingestion of a ketone monoester without co-ingestion of carbohydrate improves running economy in male endurance runners. Medicine and Science in Sports and Exercise, 2024.
Randomised controlled trial11 male runners: a ketone monoester without carbohydrate improved running economy by 4.1% compared with a carbohydrate drink, but not when taken with carbohydrate. Time to exhaustion didn't change.
doi.org/10.1249/MSS.0000000000003278 - [18]
Brady AJ, Moynagh MB, Devenney S, Egan B Advanced footwear technology, but not acute ingestion of a ketone monoester, improves running economy in middle- and long-distance runners. Medicine and Science in Sports and Exercise, 2025.
Randomised controlled trial18 trained runners, 8 of them women: a ketone monoester didn't change running economy compared with a carbohydrate drink. Advanced running shoes improved it.
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Poffé C, Ramaekers M, Van Thienen R, Hespel P Ketone ester supplementation blunts overreaching symptoms during endurance training overload. The Journal of Physiology, 2019.
Randomised controlled trial18 fit men, 3 weeks of twice-daily training: a ketone ester after each session gave a 15% higher sustainable training load in week 3 and blunted signs of overreaching.
doi.org/10.1113/JP277831 - [20]
Jameson TSO, Islam H, Wall BT, et al. Oral ketone monoester supplementation does not accelerate recovery of muscle force or modulate circulating cytokine concentrations after muscle-damaging eccentric exercise. Experimental Physiology, 2022.
Randomised controlled trial16 healthy men and women: 27 g of ketone monoester three times a day for 3 days didn't speed recovery of muscle force after muscle-damaging exercise.
doi.org/10.1113/EP090546 - [21]
Holdsworth DA, Cox PJ, Kirk T, et al. A ketone ester drink increases postexercise muscle glycogen synthesis in humans. Medicine and Science in Sports and Exercise, 2017.
Randomised controlled trial12 well-trained men, with glucose infused to hold blood glucose high: after a ketone ester drink, muscle glycogen was 50% higher than after control at the end of 2 hours' recovery.
doi.org/10.1249/MSS.0000000000001292 - [22]
Vandoorne T, De Smet S, Ramaekers M, et al. Intake of a ketone ester drink during recovery from exercise promotes mTORC1 signaling but not glycogen resynthesis in human muscle. Frontiers in Physiology, 2017.
Randomised controlled trial8 trained men: adding a ketone ester to a protein and carbohydrate recovery drink didn't change glycogen resynthesis over 5 hours.
doi.org/10.3389/fphys.2017.00310 - [23]
Clarke L, Russell SL, Spellanzon B, et al. Ketone ester ingestion increases exogenous carbohydrate storage and lowers glycemia during post-exercise recovery: a randomised crossover trial. European Journal of Nutrition, 2025.
Randomised controlled trial13 endurance-trained men, two runs to exhaustion 4 hours apart: a ketone ester in the recovery drinks raised carbohydrate stored but didn't change the second run.
doi.org/10.1007/s00394-025-03784-w - [24]
Poffé C, Robberechts R, Stalmans M, et al. Exogenous ketosis increases circulating dopamine concentration and maintains mental alertness in ultra-endurance exercise. Journal of Applied Physiology, 2023.
Randomised controlled trial18 recreational runners on a 100 km trail run, 8 of whom finished: a ketone ester kept blood BHB at about 2-3 mM and prevented the slowing of reaction times seen with placebo.
doi.org/10.1152/japplphysiol.00791.2022 - [25]
Evans M, Egan B Intermittent running and cognitive performance after ketone ester ingestion. Medicine and Science in Sports and Exercise, 2018.
Randomised controlled trial11 male team-sport athletes: a ketone ester with carbohydrate didn't change shuttle-run time to exhaustion, but limited errors in a multitasking test afterwards.
doi.org/10.1249/MSS.0000000000001700 - [26]
Robberechts R, Albouy G, Hespel P, Poffé C Exogenous ketosis improves sleep efficiency and counteracts the decline in REM sleep after strenuous exercise. Medicine and Science in Sports and Exercise, 2023.
Randomised controlled trial10 well-trained cyclists: 25 g of ketone ester after evening exercise and before sleep improved sleep efficiency by 3% and countered the exercise-induced fall in REM sleep.
doi.org/10.1249/MSS.0000000000003231 - [27]
Dearlove DJ, Harrison OK, Hodson L, et al. The effect of blood ketone concentration and exercise intensity on exogenous ketone oxidation rates in athletes. Medicine and Science in Sports and Exercise, 2021.
Randomised controlled trial6 athletes: the share of energy from burning a ketone ester peaked at about 4.5% during cycling, and doubling blood BHB didn't raise it.
doi.org/10.1249/MSS.0000000000002502 - [28]
Scott BE, Laursen PB, James LJ, et al. The effect of 1,3-butanediol and carbohydrate supplementation on running performance. Journal of Science and Medicine in Sport, 2019.
Randomised controlled trial11 male runners: a ketone precursor with carbohydrate made no difference to a 5 km time trial after 60 minutes of running, compared with carbohydrate alone.
doi.org/10.1016/j.jsams.2018.11.027 - [29]
Jo E, Silva SC, Auslander AT, et al. The effects of 10-day exogenous ketone consumption on repeated time trial running performances: a randomized-control trial. Journal of Dietary Supplements, 2022.
Randomised controlled trial32 endurance-trained adults, 10 days of ketone salts: a first 800 m run didn't change; the ketone group's average over two runs got faster, the placebo group's didn't.
doi.org/10.1080/19390211.2020.1838022 - [30]
Whitfield J, Burke LM, McKay AKA, et al. Acute ketogenic diet and ketone ester supplementation impairs race walk performance. Medicine and Science in Sports and Exercise, 2021.
Non-randomised trial18 elite race walkers: after a 5-day ketogenic diet plus a ketone ester, all nine in that group raced 10,000 m about 6% slower. Walkers chose their diet group.
doi.org/10.1249/MSS.0000000000002517 - [31]
Burke LM, Ross ML, Garvican-Lewis LA, et al. Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. The Journal of Physiology, 2017.
Non-randomised trialElite race walkers: after 3 weeks of intensified training, carbohydrate diets improved 10 km times by 5-7%; a ketogenic diet gave no gain and worse economy.
doi.org/10.1113/JP273230 - [32]
Ramos-Campo DJ, López-Román FJ, Pérez-Piñero S, et al. Effects of ketone monoester and bicarbonate co-ingestion on cycling performance in WorldTour cyclists. International Journal of Sport Nutrition and Exercise Metabolism, 2024.
Randomised controlled trial28 male WorldTour cyclists, all also taking bicarbonate: a ketone ester raised mean power in an 8-minute time trial at the start of a simulated stage by 3.1% compared with placebo.
doi.org/10.1123/ijsnem.2023-0078 - [33]
Poffé C, Ramaekers M, Bogaerts S, Hespel P Bicarbonate unlocks the ergogenic action of ketone monoester intake in endurance exercise. Medicine and Science in Sports and Exercise, 2021.
Randomised controlled trial9 well-trained male cyclists: after 3 hours of riding, 15-minute time-trial power was 5% higher only when a ketone ester was taken with bicarbonate.
doi.org/10.1249/MSS.0000000000002467 - [34]
Martí-Martí J, Navarro-Martínez D, Álvarez-Segura T, et al. Ketone supplementation in trained and physically active individuals: effects on athletic performance and metabolic variables - a systematic review. Life, 2026.
Systematic review26 controlled studies from 2018 to 2025: ketones raised blood BHB and changed acid-base balance, but performance effects were mixed. Bicarbonate sometimes helped.
doi.org/10.3390/life16071147 - [35]
Margolis LM, O'Fallon KS Utility of ketone supplementation to enhance physical performance: a systematic review. Advances in Nutrition, 2020.
Systematic review10 trials, 112 people (109 men), 16 performance outcomes: 3 positive, 10 null and 3 negative. Results varied too much to conclude a benefit or harm.
doi.org/10.1093/advances/nmz104 - [36]
NHS Vitamins, supplements and nutrition in pregnancy. NHS, 2026.
RegulatorCovers folic acid, vitamin D and iron in pregnancy, and says to speak to a GP about other supplements. Ketone supplements aren't mentioned.
www.nhs.uk/pregnancy/keeping-well/pregnancy-vitamins-and-supplements/ - [37]
Stubbs BJ, Cox PJ, Kirk T, et al. Gastrointestinal effects of exogenous ketone drinks are infrequent, mild, and vary according to ketone compound and dose. International Journal of Sport Nutrition and Exercise Metabolism, 2019.
Randomised controlled trialThree studies of ketone drinks: gut symptoms were mostly mild and short-lived, and high-dose ketone salts caused the most. Authors linked to a ketone drink maker.
doi.org/10.1123/ijsnem.2019-0014 - [38]
NHS Diabetic ketoacidosis. NHS, 2026.
RegulatorDKA is a serious condition in people with diabetes, where a lack of insulin causes ketones to build up in the blood. Gives blood ketone meter ranges: under 0.6 mmol/L normal, over 3 high.
www.nhs.uk/conditions/diabetic-ketoacidosis/ - [39]
Medicines and Healthcare products Regulatory Agency SGLT2 inhibitors: updated advice on the risk of diabetic ketoacidosis. Drug Safety Update, 2016.
RegulatorCanagliflozin, dapagliflozin and empagliflozin rarely cause diabetic ketoacidosis, sometimes with only moderately raised blood glucose.
www.gov.uk/drug-safety-update/sglt2-inhibitors-updated-advice-on-the-risk-of-diabetic-ketoacidosis - [40]
World Anti-Doping Agency The Prohibited List. World Anti-Doping Agency, 2026.
RegulatorThe substances and methods prohibited in sport. The list is not exhaustive: a substance not being named does not prove it is allowed.
www.wada-ama.org/en/prohibited-list - [41]
Maughan RJ, Burke LM, Dvorak J, et al. IOC consensus statement: dietary supplements and the high-performance athlete. British Journal of Sports Medicine, 2018.
Consensus statementSupplements can contain prohibited substances as undeclared ingredients or contaminants, and athletes are responsible for anything found in their sample.
doi.org/10.1136/bjsports-2018-099027 - [42]
Poffé C, Wyns F, Ramaekers M, Hespel P Exogenous ketosis impairs 30-min time-trial performance independent of bicarbonate supplementation. Medicine and Science in Sports and Exercise, 2021.
Randomised controlled trial14 well-trained male cyclists: a ketone ester lowered 30-minute time-trial power by 1.5%, even when bicarbonate offset the fall in blood pH.
doi.org/10.1249/MSS.0000000000002552
Who wrote and reviewed this
Written by Grant MacMillan, Editor, RunV. Not yet reviewed by an expert.
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