Caffeine
Guides, research reviews, comparisons, product recommendations and FAQs for caffeine.
Which caffeine product to buy
The dose that matters is 3-6 mg per kg of bodyweight, 45 to 60 minutes before training. What changes between products is whether the label tells you how much you are getting. The comparison page reads the panels side by side.
See the caffeine products compared →Where we send readers now
We no longer earn commission on any competing supplement brand on this page. The only supplement link we earn from is Legion, below — so you can weigh our ranking above knowing exactly where our money comes from.
- 8 g citrulline malate
- 3.6 g beta-alanine
- 350 mg caffeine
- 350 mg L-theanine
- 2.5 g betaine
- 300 mg alpha-GPC
- Every dose disclosed - no proprietary blend
- 4.6/5 from 22,589 reviews
With a subscription $37.49 — $1.87 per dose
We rated Pulse fully dosed in our own dose comparison before any commercial relationship with Legion existed. The doses are the reason, not the commission.
Check price at Legion →
- Same actives as Pulse, zero caffeine
- Every dose disclosed
Disclosure: The Iron Verdict earns a commission on purchases made through the Legion link and code above, at no extra cost to you. We were not paid to rank any product on this page, and the ratings above were written before this partnership existed.
Start with Caffeine
Best Caffeine Products
Ranked recommendations and affiliate product options.
Explore ->Caffeine Benefits Guide
Sports performance, dosage, timing, safety, sleep and practical supplement recommendations.
Explore ->Caffeine Comparisons
Compare benefits, timing, dosage and alternatives.
Explore ->Caffeine FAQs
Practical answers to common questions.
Explore ->What the Research Says
Frequently Asked Questions
What is the optimal caffeine dose for exercise?
3–6mg per kg of bodyweight is the evidence-backed pre-workout dose. For a 75kg person: 225–450mg. The dose-response plateaus above 6mg/kg and side effects (anxiety, GI issues, tachycardia) increase. For most people, 200–300mg 30–60 minutes before training is optimal. Lower doses (1–3mg/kg) also produce meaningful performance benefits with fewer side effects.
How much caffeine is too much?
The FDA considers 400mg/day safe for healthy adults. Performance benefits plateau well below that. Side effects (palpitations, anxiety, insomnia) become pronounced above 6mg/kg or >400mg. Acute toxicity (arrhythmia, seizure) has occurred at very high doses (>10g — lethal cases have involved pure powder). From food/drink: a standard coffee contains 80–180mg caffeine, energy drinks 80–300mg, pre-workouts 150–400mg.
Does caffeine tolerance develop?
Yes. With daily use, adenosine receptor upregulation occurs within 1–2 weeks, reducing caffeine's stimulant effects. 'Resetting' tolerance requires 1–2 weeks of abstinence. Strategies to preserve sensitivity: cycle caffeine (5 days on, 2 off), reserve high doses for key training sessions, or taper down over 1–2 weeks. Withdrawal symptoms (headache, fatigue) typically resolve within 3–5 days.
When is the best time to take caffeine?
30–60 minutes before training — peak plasma levels occur at 45–90 minutes. Avoid caffeine within 6–8 hours of bedtime (half-life: 5–6 hours). The 'cortisol delay' strategy (waiting until 90–120 minutes after waking before first caffeine) preserves adenosine sensitivity and may reduce afternoon crashes, though evidence is limited. Avoid immediately pre-sleep regardless of perceived tolerance.
Is caffeine bad for the heart?
At moderate doses (200–400mg/day) in healthy adults, habitual caffeine consumption is not associated with adverse cardiovascular outcomes. Prospective data actually associates 3–5 cups coffee/day with reduced cardiovascular disease risk. Paroxysmal atrial fibrillation risk increases at very high doses in some individuals. People with arrhythmias, hypertension, or pregnancy should consult a physician before high-dose caffeine use.