Caffeine
Supplements · Nootropics · Supplement, Typed Supps
You build tolerance to some of its effects faster than others.
Stage by stage
- Intake (Capsule or coffee): Absorbed quickly and almost completely in the stomach and small intestine.
- Bloodstream (Crosses into the brain): Reaches the brain within minutes.
- Brain (Blocks adenosine): Blocks adenosine, the molecule that normally signals tiredness.
- Liver (Metabolized): Broken down at a rate that varies significantly between individuals genetically.
What the evidence supports
- Improving endurance performance — strong evidence. One of the most reliably effective legal ergogenic aids there is, at roughly 3–6 mg per kg taken an hour before.
- Increasing alertness and reducing perceived effort — strong evidence. Consistent and well characterised, though tolerance to the alertness effect builds within days.
- Improving strength and power output — moderate evidence. Real but smaller and less consistent than the endurance effect.
- Producing meaningful long-term fat loss — limited evidence. It raises metabolic rate slightly and short-term, and tolerance develops. Not a weight-loss strategy.
Typical dose
50–200 mg per dose; 3–6 mg per kg of body weight before exercise for a performance effect
Upper limit: Up to 400 mg daily is considered safe for most healthy adults (FDA); 200 mg daily in pregnancy
Timing
Morning or pre-workout; avoid within ~6 hours of bedtime.
Time to effect
- 20–45 min: Noticeable effect, lasting several hours.
Medication interactions
- Ciprofloxacin and some other quinolones: Slow caffeine clearance substantially, so a normal dose hits much harder and lasts longer. (moderate)
- Theophylline: Similar mechanism and additive side effects. (high)
- Stimulant medications (including ADHD medication): Additive cardiovascular effects — raised heart rate and blood pressure. (moderate)
- Clozapine and some antidepressants: Caffeine can raise blood levels of certain psychiatric medicines. (high)
Common myth
“Tolerance means it stops working.” In reality: Tolerance reduces some effects faster than others — sleep disruption can persist even when alertness feels blunted.
Food sources
Relevant movements
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