Caffeine
Cognitive · Methylxanthine / adenosine antagonist
Tier A+
Bottom line
Read Off Label grades Caffeine as A+ (8.4/10) based on strong evidence, high benefit magnitude, and a low-risk safety profile.
Most widely used psychoactive drug.
Studied, labeled, or reported-use context: 40-400 mg/day; tolerability protocols for caffeine-naive adults commonly begin at 50-100 mg — OTC / dietary; not individualized guidance.
If you were testing this on yourself
Two properties decide whether an n-of-1 experiment is readable and recoverable. These describe the experiment — they are not a judgment about whether to run it, and nothing here is a recommendation.
Can you undo it?
Reverses on stopping
Fully reversible, though tolerance develops within days to weeks and stopping abruptly produces headache and fatigue for several days. Taper rather than stop dead if you have been using it daily.
Can you tell if it worked?
Readable — Within an hour; tolerance to the alerting effect within 1–2 weeks
Subjective alertness and any timed task you can repeat — reaction time, a work sprint, a training session.
What would fool you If you already use caffeine daily, what you are measuring is relief of withdrawal rather than a benefit over baseline — the most misread effect in this entire database. A genuine test requires a 1–2 week washout first. Sleep quality the night before dominates any next-day measure.
What the evidence says
Most widely used psychoactive drug. FDA and EFSA both treat up to ~400 mg/day as generally safe for most healthy non-pregnant adults, but timing is crucial: the ~5-hour half-life can disrupt sleep if taken after mid-afternoon. Tolerance builds rapidly and dose escalation is common. Pure or highly concentrated caffeine powders/liquids are a separate hazard because small measuring errors can be toxic or fatal. Caffeine and L-theanine have also been studied in combination for acute attention outcomes.
Mechanism
Non-selective adenosine A1/A2A receptor antagonist; blocks tonic inhibition of wake-promoting neurons; indirectly elevates dopamine/norepinephrine; cAMP elevation via PDE inhibition at high doses
Studied, labeled, or reported dose & route
40-400 mg/day; tolerability protocols for caffeine-naive adults commonly begin at 50-100 mg
This records doses and routes described in studies, approved labeling, clinical practice, or documented use. It is not individualized guidance and does not establish safety; context changes with indication, formulation, health history, monitoring, and other medicines.
Citations
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Common questions
- What does the evidence show about Caffeine's effects?
- Read Off Label rates the evidence for Caffeine as Strong and the benefit magnitude as high, producing an overall grade of A+ (8.4/10). Most widely used psychoactive drug.
- What safety findings are reported for Caffeine?
- Caffeine has a low risk profile in the database. Low (ordinary dietary use; dependence, sleep disruption, anxiety in sensitive users); Very High for pure/bulk powder misuse Legal status: OTC / dietary.
- What doses or routes are reported for Caffeine?
- 40-400 mg/day; tolerability protocols for caffeine-naive adults commonly begin at 50-100 mg This is context from studies, approved labeling, clinical practice, or documented use; it is not individualized guidance and does not establish safety.
- How does Caffeine work?
- Non-selective adenosine A1/A2A receptor antagonist; blocks tonic inhibition of wake-promoting neurons; indirectly elevates dopamine/norepinephrine; cAMP elevation via PDE inhibition at high doses
This is an independent synthesis of published research by a non-clinician. Scores are opinions supported by citations, not prescriptions. See the full disclaimer and methodology for how this score was produced and what it does and doesn't mean.