What melatonin actually is
Melatonin is a hormone, not a sedative. It is produced naturally by the pineal gland in response to darkness, and its primary role is to signal to the body that night has arrived — shifting your internal clock and preparing the brain for sleep. It does not directly induce unconsciousness the way a sleeping pill does. This distinction matters enormously when evaluating whether supplemental melatonin will help you.
Your brain's natural melatonin output at night is very small — approximately 0.1 to 0.3 milligrams. Most over-the-counter tablets contain 3mg, 5mg, or 10mg per dose. This means the average person taking a standard pharmacy tablet is consuming 10 to 100 times the amount their brain would naturally produce — a discrepancy that is rarely mentioned on the packaging.
The evidence: pros and cons
- Effective for circadian shifting. The strongest evidence for melatonin is not about sleep quality — it's about sleep timing. For jet lag and shift work, studies consistently show it accelerates adaptation to new time zones by up to 50%, helping the body clock reset faster than it would naturally.
- Reduces sleep onset latency. A 2013 meta-analysis by Ferracioli-Oda et al. in PLOS ONE, covering 19 randomised controlled trials, found melatonin reduced time to fall asleep by an average of 7 minutes. Modest, but statistically significant and consistent.
- Non-habit forming. Unlike benzodiazepines or z-drugs such as Zolpidem, melatonin does not appear to cause physiological dependence or withdrawal symptoms. You can discontinue it without rebound insomnia — a major advantage over pharmaceutical sleep aids.
- Low short-term side effect profile. At doses of 0.5–1mg, side effects are generally mild — occasional morning grogginess or vivid dreams — and typically resolve within a few days of stopping.
- Useful for delayed sleep phase disorder. People whose natural sleep timing is significantly delayed (falling asleep at 2–4am) show meaningful improvement with low-dose melatonin taken 5–6 hours before the target bedtime, helping to gradually shift the clock earlier.
- Most people take far too much. A 2023 study by Cohen et al. in JAMA analysed 25 brands of melatonin gummies sold in the US and found that 22 of them were mislabelled — with actual melatonin content ranging from 74% to 347% of the stated dose. Combined with already-high labelled doses, most users are taking 10–100× their physiological need.
- Weak evidence for general insomnia. For people who don't have a circadian disorder — they simply struggle to sleep — melatonin performs only marginally better than placebo. The effect size is small compared to Cognitive Behavioural Therapy for Insomnia (CBT-I), which produces larger and more durable improvements.
- Does not improve sleep architecture. Melatonin doesn't meaningfully increase slow-wave (deep) sleep or REM sleep duration. You may fall asleep slightly faster, but sleep quality as measured by polysomnography (brain wave monitoring) changes little.
- Label accuracy is poor. A 2017 study by Erland & Saxena in the Journal of Clinical Sleep Medicine found that melatonin content in tested supplements varied from 83% below to 478% above the labelled dose. This is a significant regulatory concern — particularly for parents giving supplements to children.
- Long-term effects are understudied. Most clinical trials run for fewer than 13 weeks. There is limited peer-reviewed data on the hormonal and receptor-level effects of taking melatonin nightly for years. As a hormone, prolonged high-dose use deserves more caution than most users apply.
What most people get wrong: the dose
The single most common error with melatonin is taking too much. Because it is sold as a dietary supplement rather than a regulated drug in most countries, manufacturers are incentivised to add more — it makes users feel the product is "working." But supraphysiological doses (those far above what the brain naturally produces) do not improve sleep further. They may actually impair melatonin receptor sensitivity over time.
The research-supported effective dose is 0.5mg to 1mg, taken 30–60 minutes before your target sleep time. This is the dose used in most clinical trials that show a real effect. It is also well below what is sold in virtually every pharmacy or supermarket.
When melatonin makes sense
Based on current evidence, melatonin is likely to be beneficial in the following situations:
Jet lag
Take 0.5–1mg at the target bedtime in your new time zone, starting on the day of travel. The evidence here is among the strongest for any melatonin application. Eastward travel (phase advancing) tends to respond better than westward travel.
Shift work
Shift workers whose sleep timing changes regularly may benefit from melatonin to anchor sleep to their off-shift rest period. Timing is critical — it should be taken at the start of the intended sleep window, not at a fixed clock time.
Delayed sleep phase disorder
For people who naturally fall asleep very late (2–4am) and struggle to advance their sleep timing, low-dose melatonin taken 5–6 hours before the target bedtime — combined with consistent morning light exposure — can gradually shift the rhythm earlier over several weeks.
Short-term use for routine disruption
Occasional use (a few days) during periods of unusual schedule disruption — early flights, long days, time zone changes — is low risk and modestly supported. Habitual nightly use for general sleep difficulty is not well supported by evidence and should not replace behavioural sleep interventions.
Melatonin works well for when you sleep — shifting your body clock for jet lag, shift work, or delayed sleep phase. It works poorly for how well you sleep. If you use it, the evidence supports the smallest effective dose (0.5–1mg), taken 30–60 minutes before your target bedtime — not at the dose printed on most pharmacy packets. For chronic insomnia without a circadian component, CBT-I has a substantially stronger evidence base and produces lasting results without any supplementation.
- Ferracioli-Oda, E. et al. (2013). Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders. PLOS ONE. View →
- Cohen, P.A. et al. (2023). Quantity of Melatonin and CBD in Melatonin Gummies Sold in the US. JAMA, 329(16), 1401–1402. View →
- Erland, L.A. & Saxena, P.K. (2017). Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content. Journal of Clinical Sleep Medicine, 13(2), 275–280. View →