How It Works
Blocks adenosine receptors (A1, A2A) → reduced perceived exertion, increased alertness. Also: increased calcium release in muscle, improved fat oxidation, enhanced Na+/K+ pump activity, dopamine/adrenaline release.
Dosage & Timing
Dosage Guide
Daily Dose3-6 mg/kg
Timing45-60 min pre-exercise. Lower doses (1-2 mg/kg) also effective for cognitive benefits.
Bioavailability99% oral absorption. Peak plasma at 30-120 min. CYP1A2 enzyme metabolizes (genetic variation — fast vs slow metabolizers).
Optimal Timing
Take with food. Consistency matters more than timing for most supplements.
Cycling & Duration
Cycle pre-workout caffeine: 8-12 weeks on, 1-2 weeks off to reset adenosine receptor sensitivity. Or use only on training days for natural reset.
Best Forms (Ranked)
Anhydrous Caffeine (pills) — ★★★★★
Precise dosing. Fast absorption. Cheapest.
Coffee — ★★★★☆
Contains additional polyphenols/antioxidants. Variable caffeine content.
Caffeine Gum — ★★★★☆
Buccal absorption. Faster onset (~10 min). Good for late-race dosing.
Evidence-Based Benefits
- 3-7% endurance performance improvement
- 5-10% strength increase
- Reduced RPE (rate of perceived exertion)
- Improved reaction time and focus
- Enhanced fat oxidation (glycogen sparing)
Side Effects & Safety
- Anxiety/jitters (dose-dependent)
- Sleep disruption (avoid within 8h of bed)
- GI distress
- Tolerance/dependence with daily use
- Heart palpitations in sensitive individuals
✅ Good For
- Almost all athletes (individual response varies)
- Pre-workout energy/focus
- Competition day performance
⚠️ Skip If
- Anxiety disorders
- Hypertension (check with doctor)
- Pregnancy (limit to <200mg/day)
- CYP1A2 slow metabolizers (may see less benefit)
Stacks Well With
Recommended Products
Affiliate links — we may earn commission.
NOW Supplements Caffeine 200mg
★★★★★ 4.7/5
L-Theanine 200mg (stack companion)
★★★★★ 4.6/5