What it is & primary uses
A central nervous system stimulant commonly studied for alertness and exercise performance.
Main benefits
- Improves alertness
- Can enhance endurance and power
- May reduce perceived exertion
Studied protocols
Research doses are grouped by outcome. They describe study designs—not a personal prescription.
3–6 mg/kg
- Study duration
- Single dose ~60 minutes before exercise
- Interpretation
- The most consistently supported ergogenic range.
1–3 mg/kg
- Study duration
- Single dose
- Interpretation
- May improve vigilance with fewer side effects for some users.
9 mg/kg
- Study duration
- Single experimental dose
- Interpretation
- Studied, but typically produces more adverse effects without reliably improving performance beyond 3–6 mg/kg.
Clinical or experimental context—professional guidance is especially appropriate.
04Food sources & equivalents＋
Can food provide a studied amount?
Coffee and tea provide caffeine, but the amount varies substantially by drink, preparation and serving size.
Roughly 210–420 mg caffeine using the FDA's 113–247 mg per-cup range
About 210–420 mg at a typical 71 mg per cup
- How this was estimated
- Example target = body weight × 3–6 mg/kg. The displayed example uses 70 kg; it is not a personal dose.
- Important limitation
- FDA notes wide product variation and cites 400 mg/day as an amount not generally associated with negative effects for most adults. Sensitivity, pregnancy, medications and sleep timing materially change the safety context.
Food equivalents compare ingredient mass using published composition values. They do not prove equal absorption, formulation, physiological effect, safety or personal need.
Source: FDA: caffeine content and safety context ↗05How to take it for absorption & tolerance＋
With or without food
Caffeine is absorbed rapidly. A meal may delay peak concentration, while dose, habitual use, genetics and timing relative to sleep matter more.
- Practical approach
- For a predictable pre-exercise effect, keep the food context consistent from one use to the next.
- Watch for
- Avoid late-day use when sleep is a priority; food does not prevent sleep disruption.
Meal guidance reflects human pharmacokinetic, clinical, official-label or evidence-review sources where available. A food pairing can change absorption or tolerability, but does not make a supplement necessary, effective or safe for every person.
Source: ISSN position stand on caffeine and exercise ↗06Supplement interaction check＋
An unlisted pair means no established pair-specific interaction was identified in this review—not proof that every dose, product or person is safe.
The combination is not proven to cancel creatine. A systematic review found mixed results: acute caffeine after creatine loading generally did not block caffeine's benefit, while chronic caffeine during loading interfered with creatine outcomes in some—but not all—studies.
No blanket avoidance rule is supported. If loading creatine, consider taking caffeine separately or reducing chronic high caffeine when gastrointestinal symptoms or a weaker training response is a concern.
Evening caffeine can delay the body's melatonin rhythm. In a small pharmacokinetic study using high doses, caffeine also substantially increased exposure to an oral melatonin dose.
Do not use melatonin simply to counter late caffeine. Keep caffeine away from the intended sleep window and review timing with a clinician for shift work or jet-lag protocols.
Human performance studies have combined caffeine and Rhodiola without showing that one cancels the other, and some reported additive performance effects. These studies do not establish long-term safety for people sensitive to stimulation.
Use earlier in the day and monitor anxiety, agitation, heart rate and sleep. Extra caution is appropriate with cardiovascular conditions or stimulant medication.
07Research notes＋
Strong for acute alertness and several exercise outcomes. Benefit and adverse effects vary markedly by dose, genetics, habituation and timing.
Response and clearance vary widely. Later-day use can impair sleep even when it does not feel disruptive.
08Scientific references＋
Peer-reviewed human research and formal evidence reviews. Open each source to inspect the complete paper record.
ISSN position stand: caffeine and exercise performance
Dose context: 3–6 mg/kg; higher and lower doses also reviewed
Supports small-to-moderate benefits across endurance, strength, sprint and vigilance outcomes; sleep and anxiety effects require attention.
Caffeine dose-response and aerobic time-trial performance
Dose context: Low 1.3–3 mg/kg and moderate 4–6 mg/kg acute doses
Both ranges improved time-trial performance; moderate doses were more consistent, while higher doses lack a clear added benefit and increase adverse-effect risk.
Acute caffeine side effects in sport
Dose context: Randomized trials across low, moderate and high acute doses
Low-to-moderate doses were associated with fewer acute side effects than doses above 6 mg/kg.
09Expert & media references＋
Podcast and practitioner statements are clearly separated from research. They may explain practice or emerging ideas, but do not prove efficacy.