Hormone
Melatonin
A hormone that regulates the sleep-wake cycle and supports circadian rhythm alignment.
KÖGN Health grades Melatonin as A+ (Strong evidence) and rates it 4.5 out of 5.
Last reviewed · June 2026
Primary effects
- Improved sleep
- Circadian rhythm regulation
- Recovery support
How it works
Signals the body to prepare for sleep, regulating circadian timing and recovery processes.
Overview
Melatonin is one of the most well-researched sleep-regulating compounds. It is particularly effective for sleep onset difficulties and jet lag, as it helps reset the body’s internal clock. While it is generally safe for short-term use, long-term daily use may reduce natural endogenous production in some individuals. It is best used strategically rather than as a permanent sleep dependency solution.
The evidence
Melatonin is the best-supported supplement for sleep onset. Meta-analyses of randomised trials find it reduces the time taken to fall asleep by a modest but consistent amount and helps re-time the body clock — making it most useful for jet lag and delayed sleep phase. It is a sleep-timing aid rather than a sedative, and not a direct cognitive enhancer; any cognitive benefit is downstream of better sleep.
How to dose it
Trials commonly use 0.5–5 mg taken 30–60 minutes before the target bedtime. More is not better — low doses (0.5–1 mg) are often as effective and cause less morning grogginess.
When to take it
Acute, and timing is the whole point: taken a few hours before bedtime it can advance the body clock; taken at the wrong time it can shift sleep the wrong way.
Safety & side effects
Well tolerated for short-term use. The usual effects are morning grogginess, vivid dreams, and headache. Long-term safety data are more limited. In the UK it is a prescription medicine, though widely sold elsewhere.
Who should avoid it
Do not drive or operate machinery after taking it. Take care alongside sedatives, anticoagulants, and immunosuppressants, and if you have an autoimmune condition. Safety in pregnancy and breastfeeding is not established — speak to a clinician.
References
Related ingredients
Graded entries that target the same cognitive goals.
Categories
Draft — the dose, safety and evidence notes on this entry were prepared from the published literature and are pending editorial and clinical review.
Educational information, not medical advice. The evidence grade is KÖGN’s editorial assessment of published research, not a health claim. Speak to a qualified clinician before changing what you take.