Caffeine is the world's most widely used stimulant, with well-proven short-term gains in alertness, reduced fatigue, and exercise endurance and strength. Possible long-term benefits for Parkinson's, blood sugar, mood, and thinking are promising but less certain. Main trade-offs — sleep disruption, anxiety, faster heartbeat, and dependence — depend heavily on dose, timing, and individual biology. (Full Review)

Protocol

Ergogenic Dose

3–6 mg/kg

Taken 45–60 min before exercise for endurance and strength

Cognitive Dose

40–200 mg

Smaller, more frequent doses for focus and alertness

Timing

Morning–early PM

Some delay the first dose 90–120 min after waking

Time to effect

Alertness & Performance

30–60 min

Acute effects after an oral dose

Tolerance

Days–2 weeks

Some effects blunt with regular daily use

Withdrawal Resolves

~1 week

After stopping regular use

Benefits

High: Increased alertness, vigilance & reduced fatigue; enhanced aerobic endurance

Medium: Improved muscle strength & power; enhanced cognitive performance; reduced Parkinson's risk; increased fat oxidation; reduced type 2 diabetes risk

Low: Reduced all-cause & cardiovascular mortality; improved mood & reduced depression risk; reduced Alzheimer's & cognitive-decline risk

Speculative: Longevity via autophagy & cellular stress pathways

Contraindications

Pharmacologic cardiac stress testing (avoid 12–24 h before)

Symptomatic cardiac arrhythmias

Uncontrolled hypertension

Severe anxiety or panic disorder

Pregnancy (limit <200 mg/day)

Fluvoxamine or clozapine

Recent acute myocardial infarction

Decompensated heart failure

Key Interactions

Strong CYP1A2 inhibitors (fluvoxamine, ciprofloxacin, cimetidine)

Other CYP1A2 substrates (clozapine, theophylline, tizanidine)

Estrogen-containing oral contraceptives & hormone therapy

MAOIs

Lithium

OTC decongestants & stimulants (pseudoephedrine, phenylephrine)

OTC combination analgesics & cold remedies with caffeine

Stimulant supplements (synephrine/bitter orange, yohimbine, ephedra, guarana, green tea extract)

Alcohol

Risk & Side Effects

High: Sleep disruption; anxiety, jitteriness & nervousness; physical dependence & withdrawal

Medium: Acute blood pressure elevation; cardiac palpitations & tachycardia; gastrointestinal upset & reflux; tolerance to effects

Low: Acute toxicity & overdose; reduced bone mineral density; adverse pregnancy outcomes; elevated intraocular pressure

Speculative: Increased cardiovascular risk in slow metabolizers

Monitoring

Marker	Target	Why
Resting blood pressure	Below ~120/80 mmHg	Detects caffeine-driven pressor effect
Resting heart rate	~50–70 bpm	Flags tachycardia or palpitation susceptibility
Fasting glucose / HbA1c	Glucose <90–99 mg/dL; HbA1c <5.4%	Contextualizes caffeine's metabolic effects
Ferritin / serum iron	Ferritin ~50–150 ng/mL	Caffeine can reduce non-heme iron absorption
Sleep metrics	~7–9 h total, latency <20 min	Captures caffeine's most important downside
CYP1A2 / ADORA2A genotype	Optional one-time test	Personalizes dose and cardiovascular caution

Cadence: Baseline, reassess ~4 weeks after a change in intake, then every 6–12 months or whenever the dose or pattern changes

Qualitative Assessment

Subjective energy and alertness across the day, including any mid-afternoon crash
Sleep quality and ease of falling asleep on higher- versus lower-intake days
Anxiety, restlessness, or jitteriness after dosing
Palpitations or awareness of heartbeat
Gastrointestinal comfort and reflux symptoms
Reliance on caffeine to function, and severity of any withdrawal headache on missed doses

Caffeine for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment