Evidence explainerCaffeine (capsules, gum and anhydrous powder)

Caffeine Before a Workout: 3 mg/kg, 15 to 60 Minutes Out, and Why It Helps Endurance Most

Caffeine is one of the few performance supplements with consistent trial support. The useful dose is smaller than many pre-workouts deliver, and the benefit is clearest in endurance work.

By Kymata Health editorial teamPublished October 9, 2026Last reviewed October 9, 2026

Medical review pending. Written by our editorial team from the studies cited below; a credentialed clinician has not reviewed it yet. Educational only, not medical advice.

Key takeaways

  • Studies that found benefits mostly used about 2 to 6 mg/kg before exercise, which is 210 to 420 mg for a 70 kg adult at 3 to 6 mg/kg; more is unlikely to help further [1].
  • In a network meta-analysis of 48 time-trial studies, low-dose capsules (about 3 mg/kg) ranked best for cutting completion time [2].
  • ODS suggests taking caffeine 15 to 60 minutes before exercise; it peaks in blood within about 45 minutes [1].
  • Benefits are clearest for endurance and long intermittent sports, less so for sprinting or lifting [1].
  • Responses vary between people; in one analysis, people with the CYP1A2 CC genotype did worse with caffeine [3].

The evidence, graded

Pulled from our monograph evidence tables. Grades follow our evidence-grading policy.

  • Grade BImprovedTime-trial performance by caffeine dose and delivery formCaffeine (capsules, gum and anhydrous powder) · Meta-analysis · n=612 · 2025 · PMID 41374083Low-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).
  • Grade BImprovedEndurance running: time to exhaustion and time trialsCaffeine (capsules, gum and anhydrous powder) · Meta-analysis · n=254 · 2022 · PMID 36615805Time 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).
  • Grade CMixedPerformance response by CYP1A2 genotypeCaffeine (capsules, gum and anhydrous powder) · Meta-analysis · n=440 · 2024 · PMID 37844569Caffeine 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.

How caffeine helps

Caffeine blocks adenosine, a brain signal with sedative-like effects, which raises arousal and reduces fatigue [1]. It also appears to lower perceived pain and effort [1].

How much: the per-kilogram math

Many studies found benefits at about 2 to 6 mg/kg of body weight before exercise; for a 70 kg (154 lb) adult, 3 to 6 mg/kg is 210 to 420 mg [1]. ODS adds that more is unlikely to help further and raises side effects [1].

Lower can be enough. A 2025 network meta-analysis of 48 studies with 612 participants found low-dose capsules (≤3 mg/kg) reduced time-trial completion time the most (SMD -0.34), ahead of moderate-dose capsules (-0.31) and moderate-dose gum (-0.30) [2]. The ISSN notes very high doses, around 9 mg/kg, bring frequent side effects and do not seem to be needed [4].

When to take it

Caffeine is absorbed quickly, even through the lining of the mouth, peaks in blood within 45 minutes and has a half-life of about 4 to 5 hours [1]. ODS suggests taking it 15 to 60 minutes before exercise [1].

The ISSN says 60 minutes before is the most common timing, and that caffeine gum may need a shorter wait than capsules [4]. With a half-life of 4 to 5 hours, an evening workout dose may still be active at bedtime [1].

What it helps most

Caffeine is more likely to help endurance activities such as running and long intermittent sports such as soccer than short, intense bouts such as sprinting or lifting [1]. In 21 trials of runners (3 to 9 mg/kg), caffeine extended time to exhaustion (g = 0.392) and slightly improved time-trial completion time [5].

Not everyone responds. In one review of 33 time trials, results ranged from 0.7% worse to 17.3% better [1]. A 2024 meta-analysis found benefit in people with CYP1A2 AA and AC genotypes but worse performance in the CC group, though only 34 people were CC and the genotype effect vanished after excluding studies with possible conflicts of interest [3].

Limits and side effects

Heavy use of 500 mg/day or more may hurt rather than help performance, and can disturb sleep and cause anxiety and irritability [1]. FDA says 400 mg/day does not usually have dangerous effects in healthy adults [1]. For the full safety picture, including powder and teens, read how much caffeine is too much.

Beta-alanine is the other common pre-workout ingredient; see beta-alanine tingling.

Quick answers

Does caffeine gum work as well as pills?

In the network meta-analysis, moderate-dose gum cut time-trial completion time about as much as moderate-dose capsules (SMD -0.30 vs -0.31) [2].

Should I cut back on coffee before a race?

Some evidence suggests caffeine helps more in people not used to it, and limiting intake to 50 mg/day or abstaining for 2 to 7 days before an event might maximize the effect, but other evidence shows no habituation effect [1].

Does caffeine dehydrate you during exercise?

ODS says caffeine does not increase urine output or sweat loss during exercise enough to hurt fluid balance [1].

Keep reading

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References

  1. [1]Dietary Supplements for Exercise and Athletic Performance: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2024.
  2. [2]Effects of Caffeine Dose and Administration Method on Time-Trial Performance: A Systematic Review and Network Meta-Analysis. Nutrients, 2025. PMID 41374083
  3. [3]Caffeine, CYP1A2 Genotype, and Exercise Performance: A Systematic Review and Meta-analysis. Med Sci Sports Exerc, 2024. PMID 37844569
  4. [4]International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr, 2021. PMID 33388079
  5. [5]Effects of Caffeine Intake on Endurance Running Performance and Time to Exhaustion: A Systematic Review and Meta-Analysis. Nutrients, 2022. PMID 36615805

Caffeine (capsules, gum and anhydrous powder) and other dietary supplements are not intended to diagnose, treat, cure or prevent any disease, and these statements have not been evaluated by the FDA. Talk to your clinician or pharmacist before starting a supplement, especially if you take prescription medicines. This page has no product or affiliate links.

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