Safety · Supplement
Caffeine: side effects, safety & interactions
Safe for most in moderation; excess causes anxiety, palpitations, and insomnia. Dependence and withdrawal (headache, fat
- Overall grade
- Grade A
- Last revised
- 0
- graded outcomes
- 0
- references listed
Assembled by the app from other entries in this library. It adds no evidence of its own — follow the links to the entries it draws on.
What is uncertain
Read off the same rows as above. Nothing here is added that the entry does not itself record.
- Watch with Melatonin: Opposing circadian signals — the afternoon cutoff protects the melatonin window.
- Watch with Iron: Cuts non-heme iron absorption ~40% — separate by 2 hours.
- Watch with Rhodiola Rosea: Both activating — stack low-dose.
The evidence in words
Safety profile
Safe for most in moderation; excess causes anxiety, palpitations, and insomnia. Dependence and withdrawal (headache, fatigue) are real. Combining multiple stimulants compounds cardiovascular strain.
Interactions to respect
Melatonin — Opposing circadian signals — the afternoon cutoff protects the melatonin window. · Iron — Cuts non-heme iron absorption ~40% — separate by 2 hours. · Rhodiola Rosea — Both activating — stack low-dose.
What Caffeine is
Caffeine is a plant alkaloid and the world's most consumed psychoactive drug. It reliably increases alertness, reduces perceived effort, and improves endurance and some strength and reaction-time measures.
The honest bottom line
A genuinely effective, cheap ergogenic and nootropic. Dose to purpose, respect the early-afternoon cutoff, and pair with theanine if it makes you jittery.
Related reading
Entries that share this one's tags or conditions.
- CaffeineThe most-used and best-evidenced cognitive and physical stimulant on earth — precise dosing and a hard afternoon cutoff are the whole skill.Evidence grade A
- Caffeine for Alertness / reaction timeEvidence grade A — Acute, tolerance-limitedEvidence grade A
- Caffeine for Endurance performanceEvidence grade A — Well establishedEvidence grade A
- Caffeine for Sleep (afternoon dosing)Evidence grade A — Degrades sleep — the key costEvidence grade A
Sources
This entry lists no references of its own — it is assembled from the entries it links to, whose sources are on their pages.
Last revised . A grade is this entry's reading of the evidence, not medical advice.