Caffeine (capsules, gum and anhydrous powder)
Summary
Caffeine at about 3-6 mg/kg before exercise gives small, consistent gains in endurance, with smaller effects on strength and power. Capsules near 3 mg/kg and caffeine gum both improved time-trial results. Responses vary, possibly by CYP1A2 genotype. FDA says 400 mg/day is not usually linked to dangerous effects; pure powder is hazardous.
Key facts
- Anhydrous caffeine capsules or tablets, caffeine gum, energy drinks, gels and pure powder; natural sources such as coffee, tea, guarana and yerba mate[1][3]
- Low-dose (≈3 mg/kg) and moderate-dose capsules and moderate-dose gum all reduced time-trial completion time in a network meta-analysis (B)[3]
- Endurance running time to exhaustion ↑ (B); time-trial performance ↑ (B); strength and power ↑ small (meta-analysis without pooled n); effect varies by CYP1A2 genotype (C)[2][3][5][4]
- About 2–6 mg/kg body weight before exercise (210–420 mg for a 70 kg adult); trials in runners used 3–9 mg/kg[1][2]
- FDA: 400 mg/day not usually linked to dangerous effects in healthy adults. One tablespoon of pure powder contains about 10 g; 10–14 g can be fatal[1]
- WADA does not limit caffeine; the IOC and NCAA set urine thresholds (12 and 15 mcg/mL)[1]
- 3 graded human outcomes on this page
- October 8, 2026
How it works
EstablishedCaffeine blocks adenosine receptors, removing adenosine's sedative-like effect on the brain, muscles and heart; this raises arousal and vigor and lowers fatigue, perceived pain and perceived exertion (established). It may also mobilize fatty acids and spare muscle glycogen early in endurance exercise (proposed). Caffeine peaks in blood within about 45 minutes and has a half-life of about 4–5 hours.[1]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Time-trial performance by caffeine dose and delivery form | Improved | Grade B | Meta-analysis · n = 612 · 2025 Participants in 48 time-trial studies Form: capsules (low and moderate dose) and caffeine gum · Dose: Low dose ≈3 mg/kg capsules ranked highest; moderate-dose capsules and gum also effective · Duration: Single pre-exercise doses Low-dose capsules reduced completion time (SMD -0.34; 95% CI -0.62 to -0.06), followed by moderate-dose capsules (-0.31) and moderate-dose gum (-0.30); low-dose capsules also raised mean power output (SMD 0.38). | 41374083 (opens PubMed)Source [3] |
| Endurance running: time to exhaustion and time trials | Improved | Grade B | Meta-analysis · n = 254 · 2022 Recreational and trained runners in 21 randomized controlled trials (mostly men) Form: caffeine (forms varied) · Dose: 3 to 9 mg/kg · Duration: Single pre-exercise doses Time to exhaustion improved with caffeine (g = 0.392; medium effect) in both recreational and trained runners, and time-trial completion time fell slightly (g = -0.101). | 36615805 (opens PubMed)Source [2] |
| Performance response by CYP1A2 genotype | Mixed | Grade C | Meta-analysis · n = 440 · 2024 Participants in 13 studies genotyped for CYP1A2 (233 AA, 175 AC, 34 CC) Form: caffeine · Dose: Varied across studies · Duration: Single pre-exercise doses Caffeine improved performance in AA (SMD 0.30) and AC (SMD 0.16) genotypes but worsened it in CC (SMD -0.22). After excluding studies with a risk of conflict of interest, genotype no longer mattered. | 37844569 (opens PubMed)Source [4] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Anhydrous caffeine capsules or tablets | Varies[1] | Rapidly absorbed; peaks in blood within about 45 minutes, half-life about 4–5 hours (ODS). Low (≈3 mg/kg) and moderate doses improved time trials.[1][3] | Insomnia, restlessness, anxiety, nausea and fast heart rate with high intakes.[1] | Most performance trials |
| Caffeine chewing gum | Varies[3] | Caffeine is absorbed even through the lining of the mouth (ODS); moderate-dose gum improved time-trial completion time.[1][3] | No form-specific tolerance data in our sources.[1] | Time trials |
| Pure powdered caffeine | Varies[1] | No head-to-head human data in our sources.[1] | Very potent: 10–14 g can be fatal, and at least two young men have died after taking an unknown amount.[1] | Not studied in the trials graded here |
| Energy drinks, shots and gels; coffee and tea | Varies[1] | No head-to-head human data in our sources.[1] | Often combined with other stimulants, which may increase adverse effects.[1] | Common real-world sources |
Studied doses
Doses studied in human trials ranged from about 3 to 6 mg/kg of body weight (about 210 to 420 mg for a 70 kg adult) as single servings before exercise; some running trials used up to 9 mg/kg. More is unlikely to help further and raises side effects.[1][2][3]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Other supplements
- Other stimulantsNIH fact sheetCombining caffeine with other stimulants could increase the potential for adverse effects.[1]
Who should be careful
- High intakes
- Heavy use (500 mg/day or more) may impair rather than enhance performance and can disturb sleep and cause irritability, anxiety, restlessness, nausea, vomiting, fast heart rate and irregular rhythm. FDA says 400 mg/day is not usually linked to dangerous effects in healthy adults.[1]
- Pure powdered caffeine
- Powdered caffeine is extremely potent: a tablespoon holds about 10 g, and 10–14 g can be fatal. Deaths have been reported.[1]
- Children and teens
- The American Medical Association advises adolescents to keep caffeine to 100 mg/day or less, and the American Academy of Pediatrics says caffeinated energy drinks have no place in children's or adolescents' diets.[1]
- Before you start
- Talk to your pharmacist or clinician before adding this supplement, especially if you take prescription medicines, are pregnant or breastfeeding, or have a chronic health condition.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Articles about Caffeine (capsules, gum and anhydrous powder)
Plain-English answers to common questions, built on the evidence above.
- Caffeine Before a Workout: 3 mg/kg, 15 to 60 Minutes Out, and Why It Helps Endurance Most
- How Much Caffeine Is Too Much? 400 mg a Day, 100 mg for Teens, and Why Pure Powder Is Dangerous
- Is the Taurine in Energy Drinks Bad for You? The Safety Data Points at the Caffeine
- L-Theanine and Caffeine: What the "Calm Focus" Stack Actually Did in Trials
Frequently asked questions
How much caffeine improves exercise performance?
Most studies used about 3–6 mg per kg of body weight (about 210–420 mg for a 70 kg adult) 15–60 minutes before exercise, per ODS. A 2025 network meta-analysis found low-dose capsules near 3 mg/kg among the most effective for time trials. The ISSN position stand notes very high doses (around 9 mg/kg) bring frequent side effects without being needed for a benefit.[1][3][7]
Does caffeine help strength or only endurance?
Effects are clearest for endurance. A 2018 meta-analysis found small improvements in maximal strength (mainly upper body) and jump power, and ODS notes caffeine is less likely to help short sprints or lifting than endurance or intermittent sports.[5][6][1]
Is caffeine gum as good as pills?
In a network meta-analysis of 48 time-trial studies, moderate-dose gum improved completion time about as much as moderate-dose capsules. Caffeine is absorbed partly through the lining of the mouth.[3][1]
Why does caffeine work for some people and not others?
Habituation, timing, dose and form may all matter, and a 2024 meta-analysis found people with the CYP1A2 CC genotype performed worse with caffeine, although that finding weakened after excluding studies with possible conflicts of interest.[1][4]
Is caffeine allowed in sport?
WADA does not limit caffeine. The IOC allows caffeine up to a urine concentration of 12 mcg/mL and the NCAA prohibits amounts producing more than 15 mcg/mL; about 500 mg can reach 15 mcg/mL within 2–3 hours.[1]
Sources
- [1]Dietary Supplements for Exercise and Athletic Performance: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2024. fact-sheet
- [2]Effects of Caffeine Intake on Endurance Running Performance and Time to Exhaustion: A Systematic Review and Meta-Analysis.. Nutrients, 2022. meta-analysis
- [3]Effects of Caffeine Dose and Administration Method on Time-Trial Performance: A Systematic Review and Network Meta-Analysis.. Nutrients, 2025. meta-analysis
- [4]Caffeine, CYP1A2 Genotype, and Exercise Performance: A Systematic Review and Meta-analysis.. Med Sci Sports Exerc, 2024. meta-analysis
- [5]Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis.. J Int Soc Sports Nutr, 2018. meta-analysis
- [6]The Effect of Acute Caffeine Ingestion on Endurance Performance: A Systematic Review and Meta-Analysis.. Sports Med, 2018. meta-analysis
- [7]International society of sports nutrition position stand: caffeine and exercise performance.. J Int Soc Sports Nutr, 2021. guideline
What changed
- First draft. Every evidence-row PMID checked with NCBI E-utilities (esummary + efetch abstract) and re-read in an independent adversarial pass.