Supplement
Melatonin
Hormone · Sleep hormone
Melatonin shortens the time it takes to fall asleep – most clearly where the internal clock runs against the desired sleep time: in delayed sleep phase syndrome by 38.8 minutes, and for jet lag across at least five time zones, 9 of 10 randomized trials showed an effect. In ordinary insomnia, by contrast, the effect is small: the largest meta-analysis puts it at around seven minutes.
What melatonin is
Melatonin is a hormone made by the body, released in darkness, that controls the day-night rhythm. In foods it occurs only in trace amounts, for example in cherries and pistachios. As a food supplement, market doses according to the BfR range from 0.1 to 3 mg; online, products of up to 10 mg are available.
In the BK-Score it gets 7 out of 10 points for human evidence and 9 out of 10 for mechanism. Long-term data are largely lacking, and the usual commercial doses are well above what parts of the studies use.
How it works
Melatonin shifts and stabilizes the circadian rhythm, that is, the internal clock. This chain of action is quantified in humans. It explains why the substance works most strongly where the internal clock runs against the desired sleep time – with time zone changes and with a shifted sleep phase.
As a sleep aid in ordinary insomnia, by contrast, the effect is small. The authors of the largest meta-analysis explicitly describe it as smaller than that of established sleeping pills.
What is well supported
- Jet lag across five or more time zones: the most robust use case. In the Cochrane review by Herxheimer 2002, melatonin reduced jet lag in 9 of 10 randomized trials, taken close to the target bedtime between 10 p.m. and midnight. The participants were airline passengers, flight crew and military personnel. There are no pooled effect sizes; the data date from 2002.
- In delayed sleep phase syndrome, the effect is large. Buscemi 2005 puts the reduction in time to fall asleep there at 38.8 minutes (−50.3 to −27.3) – compared with 7.2 minutes in insomnia. This breakdown is based on 2 studies.
- Three endpoints, all significant, across 19 randomized trials. Ferracioli-Oda 2013 analyzed 1,683 adults and children with primary sleep disorders: time to fall asleep 7.06 minutes shorter (4.37 to 9.75; p less than 0.001), total sleep time +8.25 minutes (1.74 to 14.75; p = 0.013), sleep quality SMD 0.22 (0.12 to 0.32; p less than 0.001). With continued use, the effect did not wane. The authors explicitly describe it as smaller than that of established sleeping pills.
- The dose question has been answered. In the Cochrane review, 0.5 to 5 mg worked similarly; at 5 mg, participants fell asleep faster and slept better than at 0.5 mg, and above 5 mg there was no additional benefit. A 2 mg slow-release form was relatively ineffective. The mechanism behind it – the shift of the circadian rhythm – is quantified in humans and gets 9 out of 10 points in the BK-Score.
What the studies show
Seven minutes: the figure from the largest meta-analysis
Ferracioli-Oda 2013 analyzed 19 randomized placebo-controlled trials with 1,683 adults and children with primary sleep disorders. Time to fall asleep shortened by 7.06 minutes (95 % interval 4.37 to 9.75; p less than 0.001), total sleep time rose by 8.25 minutes (1.74 to 14.75; p = 0.013), and sleep quality by SMD 0.22 (0.12 to 0.32; p less than 0.001). Higher doses and longer use had stronger effects, and the effect did not wane with continued use.
Broken down: where the effect is large and where it is not
For short-term use of up to four weeks in primary sleep disorders, Buscemi 2005 found an overall 11.7 minutes shorter time to fall asleep (−18.2 to −5.2). The breakdown is the real finding: in delayed sleep phase syndrome it was −38.8 minutes (−50.3 to −27.3; 2 studies), in insomnia, by contrast, only −7.2 minutes (−12.0 to −2.4; 12 studies). The authors concluded that melatonin is not effective in the short term for most primary sleep disorders.
Jet lag: the most robust use case
A Cochrane review by Herxheimer 2002 analyzed 10 randomized trials in airline passengers, flight crew and military personnel. In 9 of 10 trials, melatonin taken close to the target bedtime, that is, between 10 p.m. and midnight, reduced jet lag across at least five time zones. On dose: 0.5 to 5 mg worked similarly; at 5 mg, participants fell asleep faster and slept better than at 0.5 mg, and above 5 mg there was no additional benefit. A 2 mg slow-release form was relatively ineffective. There are no pooled effect sizes; the data date from 2002.
Where the data stop
- A clinically relevant effect in ordinary insomnia. Seven minutes less time to fall asleep is statistically significant, but the authors themselves describe the effect as smaller than that of established sleeping pills. Buscemi 2005 considers melatonin not effective in the short term for most primary sleep disorders.
- Benefit of higher doses for jet lag. Above 5 mg, the Cochrane review found no additional effect. According to the BfR, products sold online go up to 10 mg.
- Benefit on flights across few time zones. The jet lag finding applies from at least five time zones crossed. Below that, these studies provide no evidence.
Status, approval and legal
In the EU, melatonin is also approved as a medicine, among other things as a 2 mg slow-release tablet for the short-term treatment of primary insomnia from age 55; in Germany, it is prescription-only as a medicine. Alongside this, it is sold freely as a food supplement. The German Federal Institute for Risk Assessment assessed melatonin in its statement 42/2024 of September 17, 2024. Key message: a robust health-based maximum level cannot be derived. The BfR advises against use in children and adolescents, during pregnancy and breastfeeding, and in liver and kidney dysfunction, autoimmune diseases and epilepsy.
Safety
As reported side effects, the BfR lists drowsiness, headache, prolonged reaction time, drop in blood pressure, nightmares and morning grogginess. The prolonged reaction time matters in everyday life, for example in road traffic. In the BK-Score, safety gets 7 out of 10 points, partly because long-term data are largely lacking. This text is for information and does not replace medical advice.
BK-Score Supported, with caveats
| Human evidence | 7 | |
|---|---|---|
| Mechanism | 9 | |
| Safety data | 7 | |
| Hype gap | 6 | |
| Track record of use | 9 |
The circadian chain of action is quantified in humans, and there are meta-analyses on time to fall asleep and on jet lag. Long-term data are largely lacking, and the doses common in Germany are well above what the studies use.
The score rates the state of knowledge, not the substance. “Safety data 9” means well studied – not harmless. “Track record of use 9” means used long and widely – that is not proof of efficacy.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)
Frequently asked questions about melatonin
How does melatonin work?
Melatonin is the body's own signal for darkness and shifts and stabilizes the internal clock. This chain of action is quantified in humans. It explains why the substance works most strongly where the internal clock runs against the desired sleep time, that is, with jet lag and with a shifted sleep phase.
How much faster do you fall asleep with melatonin?
On average, about seven minutes. The largest meta-analysis, with 19 randomized trials and 1,683 participants, found a 7.06 minutes shorter time to fall asleep and 8.25 minutes more total sleep. Both values are statistically significant. The authors, however, explicitly describe the effect as smaller than that of established sleeping pills.
Does melatonin help with jet lag?
This is where the data are best. A Cochrane review of ten randomized trials in airline passengers, flight crew and military personnel found a reduction in jet lag in nine of ten trials when melatonin was taken close to the target bedtime between 10 p.m. and midnight. The finding applies from at least five time zones crossed.
Does a higher dose do more?
Not above five milligrams. The Cochrane review on jet lag found similar efficacy between 0.5 and 5 milligrams, with five milligrams leading to faster sleep onset than 0.5 milligrams. Above five milligrams, there was no additional benefit. According to the German Federal Institute for Risk Assessment, products of up to ten milligrams are sold online.
Is melatonin allowed in Germany?
In Germany, melatonin is sold as a food supplement, with market doses between 0.1 and 3 milligrams. In 2024, the German Federal Institute for Risk Assessment concluded that no robust health-based maximum level can be derived. Among others, it advises children and adolescents as well as pregnant and breastfeeding women against use. There is also a prescription-only medicine with 2 mg in slow-release form for people aged 55 and over with primary insomnia.
What side effects does melatonin have?
Reported effects include drowsiness, headache, prolonged reaction time, drop in blood pressure, nightmares and morning grogginess. The prolonged reaction time in particular matters in everyday life. The German Federal Institute for Risk Assessment advises against use in liver and kidney dysfunction, autoimmune diseases and epilepsy. This information does not replace medical advice.
The podcast episode (in German)
Episode 55
Melatonin: the darkness hormone fact-checked
The podcast by Paul Höser (Episode 55) · with Paul & Paula. The world's best-selling sleep aid, used correctly: a chronobiotic instead of a sleeping pill, the less-is-more dose (Wurtman/MIT: 0.3–1 mg), honestly quantified meta-analyses, jet lag (supported by Cochrane), shift work, the night-owl protocol with an early mini-dose, its second identity as a mitochondrial antioxidant, and red light between physics and marketing. Information only, no dosage or usage recommendation.
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Sources
- Ferracioli-Oda 2013, PLoS ONE – meta-analysis, 19 RCTs, primary sleep disorders (PMID 23691095)
- Buscemi 2005, Journal of General Internal Medicine – meta-analysis, short-term use (PMID 16423108)
- Herxheimer 2002, Cochrane Database of Systematic Reviews CD001520 – jet lag, 10 RCTs (PMID 12076414)
- BfR statement 42/2024 of September 17, 2024 – melatonin-containing food supplements
Open in the database – with search, filters and comparison (German app)
Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-10-04.