SupplementWell-studiedStimulant

Caffeine

Half-life

5–6 hours

What is Caffeine?

Most widely consumed psychoactive substance. Adenosine receptor antagonist producing wakefulness and performance benefits.

How Caffeine works

Competitive antagonist at adenosine A1 and A2A receptors — blocking fatigue signals. Increases dopamine, norepinephrine, and acetylcholine release. Stimulates lipolysis and spares glycogen during exercise.

Benefits & uses

Common uses: Alertness, cognitive performance, athletic endurance, fat oxidation, mood enhancement.

CognitiveFat Loss

Caffeine dosage

Typical dose: 3–6 mg/kg body weight for performance (200–400 mg). Avoid >2 pm. Cycle breaks recommended.

Caffeine half-life

5–6 hours (individual variation 3–9 hours based on CYP1A2 genotype)

Caffeine side effects

Anxiety, jitteriness, elevated heart rate, sleep disruption. Dependency with chronic use.

Anxiety and jitteriness (especially without L-theanine)
Elevated heart rate and blood pressure
Sleep disruption — respect 6-hour cutoff
Dependency and withdrawal headaches
GI upset on empty stomach
Jitters/anxiety
Insomnia if late
Raised heart rate
Dependence/withdrawal headaches
Tolerance

Warnings & monitoring

Tolerance + dependence build; avoid late-day dosing. Caution with anxiety/heart conditions.

Caffeine interactions

with Clenbuterol
Caution · moderate
Both caffeine and clenbuterol are stimulants with cardiovascular effects (increased heart rate, blood pressure). Combining them amplifies tachycardia risk and can cause tremors and anxiety.
Timing: Minimize caffeine intake while using clenbuterol to avoid additive cardiovascular strain
with Ephedrine
Caution · moderate
The ECA stack is a classic thermogenic combination. Ephedrine is a sympathomimetic; caffeine potentiates its effects. Additive cardiovascular load — not appropriate for those with hypertension or cardiac issues.
Timing: ECA stack: Ephedrine 25mg + Caffeine 200mg + Aspirin 81mg; limit to 2–3×/day
with Yohimbine
Caution · moderate
Yohimbine's alpha-2 antagonism plus caffeine's adenosine block can cause anxiety, palpitations, and panic episodes in sensitive users.
Timing: Fasted cardio stack — Yohimbine 0.2mg/kg + caffeine 100–200mg
with Creatine
Compatible
Older claims of caffeine blunting creatine were debunked; performance studies show additive ergogenic effect when both are dosed routinely.
Timing: Pre-workout — caffeine 30 min prior, creatine post-workout

Commonly stacked with

L-Theanine

Track Caffeine in Protokol.

Log doses, model half-lives, check interactions, and line it all up against your bloodwork. Free on iPhone and Android.