Caffeine 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 it does, modestly: a meta-analysis of 21 trials in runners found caffeine improved time to exhaustion and made time trials slightly faster[1]. Studies consistently found benefits at 3 to 6 mg per kg of body mass, most often taken an hour before exercise[2], and responses vary between people[3].
- Research
- Strong (proposed)Longer time to exhaustion, and small gains when time trials are pooled. Responses vary between people.
- 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: not studied
What is caffeine?
Caffeine is a stimulant found in coffee and tea, and in products athletes use such as caffeinated gels, chews, gum and energy drinks[2].
The Australian Institute of Sport puts caffeine in Group A of its supplement framework, meaning strong scientific evidence for use in specific situations in sport[4].
Also called: coffee, caffeine tablets, caffeinated gels.
Why is caffeine getting attention?
Caffeine is one of the most widely used performance-enhancing substances in sport[1], and one of the few supplements the IOC consensus statement says has good evidence behind it[5].
The international athletics federation's 2019 consensus lists it among the evidence-based supplements for athletics[6].
How does caffeine work?
Its main effect is thought to be on the brain and nervous system, partly by blocking adenosine receptors, though other mechanisms have been proposed too[2].
It is absorbed quickly from the gut and peaks in the blood 30 to 120 minutes after it is taken; studies most often gave it 60 minutes before exercise[2].
Does caffeine improve running performance?
Yes, modestly: in a meta-analysis of 21 trials in runners, time to exhaustion improved and time trials got slightly faster when all the trials were pooled[1].
800 m to 5K (Studied)
Well-trained and recreational runners ran a 5 km time trial about 1% faster after caffeine than after a placebo[7]. In the running meta-analysis, time trials from 800 m to 5 km weren't significantly faster when analysed on their own[1].
10K to half marathon (Limited research)
In the running meta-analysis, time trials longer than 5 km, including four at 10 km and one at 21 km, showed no significant improvement when analysed on their own; the small overall benefit came from pooling all distances[1]. Across endurance exercise in general, the ISSN finds caffeine's most consistent benefits[2].
Marathon (Not studied)
We found no controlled trials in marathons. Most of the evidence for endurance comes from cycling in the laboratory[1].
Ultra (Not studied)
We found no controlled trials in ultra running; the evidence comes from shorter tests[1].
The key studies, in order
- 2008Trial30 runners: 5 km time trials were about 1% faster after 5 mg/kg of caffeine than after a placebo, in both well-trained and recreational runners. [7]
- 2018Trial101 athletes, 10 km cycling: caffeine helped those with the AA version of the CYP1A2 gene, did nothing for AC and slowed CC at the higher amount. [3]
- 2018ConsensusCaffeine is among the few performance supplements with good evidence. Contamination is a known anti-doping risk of supplement products. [5]
- 2019ConsensusEvidence-based supplements for athletics include caffeine, bicarbonate, beta-alanine, nitrate and creatine, with value specific to each event. [6]
- 2020Meta-analysisAcross 21 meta-analyses, caffeine improved aerobic endurance, strength and power, with moderate-quality evidence; most studies were in young men. [8]
- 2021ConsensusMost consistent benefits for aerobic endurance; 3-6 mg/kg improved performance; very high amounts brought side effects; responses vary with genetics and habitual intake. [2]
- 2022Meta-analysis21 randomised trials in runners (254 people, 220 men): caffeine improved time to exhaustion (medium effect) and time-trial times (small effect). [1]
What the research can't tell us yet
Most participants were men: 220 of 254 in the running meta-analysis[1]. The quality of evidence across published meta-analyses was mostly rated moderate[8].
Responses vary. In a trial of 101 athletes, caffeine helped those with one version of the CYP1A2 gene, did nothing for another and slowed a third[3].
How is caffeine used in studies?
Caffeine has consistently improved performance in studies at 3 to 6 mg per kg of body mass. The lowest effective amount may be around 2 mg per kg, and very high amounts, such as 9 mg per kg, brought more side effects without being needed[2].
It was most often taken 60 minutes before exercise; caffeinated gum may act faster than capsules[2].
| What studies used | When | Ref. |
|---|---|---|
| 3 to 6 mg per kg of body mass | Most often 60 minutes before exercise | [2] |
| 5 mg per kg of body mass | Before a 5 km time trial | [7] |
What are the side effects, and who should be careful?
Caffeine can disrupt sleep and cause feelings of anxiety or jitteriness in some people, differences the ISSN links partly to genetics[2].
Very high amounts, around 9 mg per kg, brought a high rate of side effects in studies[2].
In pregnancy, the NHS says no more than 200 mg of caffeine a day[9].
Be careful if
- You're pregnant: the NHS says no more than 200 mg of caffeine a day[9].
- You train or race late in the day: caffeine can disrupt sleep[2].
- Caffeine makes you anxious or jittery: responses vary between people[2].
Is caffeine allowed in competition?
Caffeine is not on the World Anti-Doping Agency's Prohibited List[10]. It was removed from WADA's controlled substances in 2004[2] and is in WADA's Monitoring Program, which tracks use without prohibiting it[10].
The ISSN notes that athletes are encouraged to keep urine caffeine below 12 µg per ml, the old doping limit. That corresponds to about 10 mg per kg taken over several hours, more than three times the amounts shown to improve performance[2].
The anti-doping risk with any supplement product is contamination: products can contain prohibited substances that aren't on the label, and athletes are responsible for anything found in their sample[5].
Independent quality-assurance schemes, often called batch testing, check supplement products for prohibited substances[5]. WADA says using a product from one of these schemes can reduce, but not eliminate, the risk of an anti-doping violation[10], and the IOC says no product can be guaranteed entirely safe[5].
Myth or evidence?
5 things runners hear about caffeine. Pick an answer to see what the research says.
1.Caffeine improves endurance running performance.
Show the answer
Evidence. A meta-analysis of 21 trials in runners found better time to exhaustion and slightly faster time trials[1].
2.More caffeine always means a bigger improvement.
Show the answer
Myth. Very high amounts, such as 9 mg per kg, brought more side effects and don't seem to be needed[2].
3.Everyone responds to caffeine in the same way.
Show the answer
Myth. In one trial, the effect depended on a gene that affects caffeine metabolism[3].
4.Caffeine is banned in athletics.
5.Caffeine can disrupt your sleep.
Show the answer
Evidence. Disrupted sleep is one of the side effects the ISSN describes[2].
Have you tried caffeine?
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Frequently asked questions
- Does caffeine improve running performance?
- Research suggests it does, modestly: in a meta-analysis of 21 trials in runners, time to exhaustion improved and time trials got slightly faster[1].
- How long before a run do studies give caffeine?
- Most often 60 minutes before exercise; caffeinated gum may act faster[2].
- Why does caffeine work for some runners and not others?
- Genes play a part: in one trial, caffeine helped athletes with one version of the CYP1A2 gene and not others[3]. Habitual intake may matter too[2].
- Is caffeine banned in athletics?
- No. It is not on the WADA Prohibited List and has been monitored rather than controlled since 2004[10][2].
- Can caffeine affect sleep?
- Yes. Disrupted sleep and anxiety are among the side effects the ISSN describes[2].
References
- [1]
Wang Z, Qiu B, Gao J, Del Coso J Effects of caffeine intake on endurance running performance and time to exhaustion: a systematic review and meta-analysis. Nutrients, 2022.
Meta-analysis21 randomised trials in runners (254 people, 220 men): caffeine improved time to exhaustion (medium effect) and time-trial times (small effect).
doi.org/10.3390/nu15010148 - [2]
Guest NS, VanDusseldorp TA, Nelson MT, et al. International society of sports nutrition position stand: caffeine and exercise performance. Journal of the International Society of Sports Nutrition, 2021.
Consensus statementMost consistent benefits for aerobic endurance; 3-6 mg/kg improved performance; very high amounts brought side effects; responses vary with genetics and habitual intake.
doi.org/10.1186/s12970-020-00383-4 - [3]
Guest N, Corey P, Vescovi J, El-Sohemy A Caffeine, CYP1A2 genotype, and endurance performance in athletes. Medicine and Science in Sports and Exercise, 2018.
Randomised controlled trial101 athletes, 10 km cycling: caffeine helped those with the AA version of the CYP1A2 gene, did nothing for AC and slowed CC at the higher amount.
doi.org/10.1249/MSS.0000000000001596 - [4]
Australian Institute of Sport AIS Sports Supplement Framework: Group A and linked fact sheets. Australian Sports Commission, 2026.
Consensus statementLists caffeine in Group A: strong scientific evidence for use in specific situations in sport, using evidence-based protocols.
www.ausport.gov.au/ais/nutrition/supplements/group_a - [5]
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 statementCaffeine is among the few performance supplements with good evidence. Contamination is a known anti-doping risk of supplement products.
doi.org/10.1136/bjsports-2018-099027 - [6]
Burke LM, Castell LM, Casa DJ, et al. International Association of Athletics Federations consensus statement 2019: nutrition for athletics. International Journal of Sport Nutrition and Exercise Metabolism, 2019.
Consensus statementEvidence-based supplements for athletics include caffeine, bicarbonate, beta-alanine, nitrate and creatine, with value specific to each event.
doi.org/10.1123/ijsnem.2019-0065 - [7]
O'Rourke MP, O'Brien BJ, Knez WL, Paton CD Caffeine has a small effect on 5-km running performance of well-trained and recreational runners. Journal of Science and Medicine in Sport, 2008.
Randomised controlled trial30 runners: 5 km time trials were about 1% faster after 5 mg/kg of caffeine than after a placebo, in both well-trained and recreational runners.
doi.org/10.1016/j.jsams.2006.12.118 - [8]
Grgic J, Grgic I, Pickering C, et al. Wake up and smell the coffee: caffeine supplementation and exercise performance, an umbrella review of 21 published meta-analyses. British Journal of Sports Medicine, 2020.
Meta-analysisAcross 21 meta-analyses, caffeine improved aerobic endurance, strength and power, with moderate-quality evidence; most studies were in young men.
doi.org/10.1136/bjsports-2018-100278 - [9]
NHS Foods to avoid in pregnancy. NHS, 2026.
RegulatorIn pregnancy, no more than 200 mg of caffeine a day; too much has been linked to a higher chance of miscarriage and stillbirth.
www.nhs.uk/pregnancy/keeping-well/foods-to-avoid/ - [10]
World Anti-Doping Agency The Prohibited List. World Anti-Doping Agency, 2026.
RegulatorThe substances and methods prohibited in sport. Caffeine is not on it.
www.wada-ama.org/en/prohibited-list
Who wrote and reviewed this
Written by Grant MacMillan, Editor, RunV. Not yet reviewed by an expert.
Last checked against its references . Next review due . How pages are reviewed · How we grade research
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