Quick answer
NCCIH lists headache among the mild side effects reported in short-term studies. A systematic review of 37 trials reported headache at 0.74%, behind daytime sleepiness at 1.66%, with few serious events. At doses of 10 mg or more, another review found more adverse events than placebo. Ask your doctor about frequent headaches.1,2,3
Key facts
- NCCIH lists headache, dizziness, nausea and sleepiness as the mild side effects reported in short-term studies in adults.1
- A systematic review of 37 randomized trials found daytime sleepiness (1.66%), headache (0.74%) and dizziness (0.74%) among the most frequent adverse events.2
- Most of those events cleared on their own within a few days or when melatonin was stopped.2
- In four low-risk-of-bias trials of 10 mg or more, melatonin appeared to raise the rate of adverse events such as drowsiness, headache and dizziness, with a rate ratio of 1.40.3
- Nightmares were among the few events a systematic review rated serious or clinically significant, and they were rare.2
What does NCCIH say about melatonin and headaches?
NCCIH lists headache among the mild side effects. It cites a 2015 review of short-term studies in adults, surgical patients and critically ill patients, which found headache, dizziness, nausea and sleepiness. It lists headache again among the effects reported in children, and says the possible long-term side effects are unclear.1
Side effects reported in short-term studies in adults were mild: headache, dizziness, nausea and sleepiness.1,4
How often does it happen?
A 2019 systematic review gives the clearest numbers. It pooled 37 randomized, placebo-controlled trials of melatonin for sleep disorders, with daily doses of 0.15 mg to 12 mg and follow-up of up to 29 weeks, though most trials lasted 4 weeks or less.2
| Event | Frequency reported by the review |
|---|---|
| Daytime sleepiness | 1.66% |
| Headache | 0.74% |
| Other sleep-related events | 0.74% |
| Dizziness | 0.74% |
| Low body temperature | 0.62% |
Read the percentages as rough frequencies, not personal odds: the abstract does not spell out what they are a share of, and the review found that many trials predated reporting standards or reported poorly. Most events resolved within days or when treatment stopped, and the review found none that were life threatening.2
Do higher doses cause more headaches?
A 2022 systematic review and meta-analysis looked at doses of 10 mg or more in adults. It identified 79 studies with 3,861 participants, but 29 of them said nothing about adverse events, and only four met its low-risk-of-bias criteria for pooling. In those four, melatonin did not detectably raise serious adverse events, but did appear to raise the rate of adverse events such as drowsiness, headache and dizziness, with a rate ratio of 1.40.3
The authors cautioned that their confidence limits were wide because so little suitable data exist. That limits what can be said: the abstracts we read do not compare amounts head to head, so the sources do not show whether lower amounts cause fewer headaches. They show only that the lowest-risk trials at high doses had more events than placebo.3
What about nightmares and other effects people ask about?
The 2019 review listed nightmares among a small group of events it considered serious or clinically significant, together with agitation, fatigue, mood swings, skin irritation and palpitations, and said very few such events occurred. NCCIH does not list nightmares or vivid dreams among the side effects it names.1,2
Older people may notice more next-day effects, because NCCIH says melatonin may stay active longer in them than in younger people and cause daytime drowsiness.1
Melatonin may stay active longer in older people than in younger people and cause daytime drowsiness.1
Who should ask a doctor?
- Anyone who gets frequent or severe headaches after starting melatonin should ask a doctor whether the supplement could be involved.
- Anyone on a blood thinner or with epilepsy should ask before using melatonin, because NCCIH advises medical supervision.1
- Anyone who gives melatonin to a child should ask the pediatrician, since the effects of long use in children are not known.1
- Anyone using a higher amount than a product's label suggests should say so, because the amounts in supplements often differ from the label.
Questions people ask
Does melatonin cause nightmares?
A 2019 systematic review of 37 trials listed nightmares among a few rare events it rated serious or clinically significant. NCCIH does not list nightmares as a side effect.1,2
Does melatonin cause dementia?
None of the sources we read report that melatonin causes dementia. NCCIH notes that 2015 guidelines from the American Academy of Sleep Medicine recommend against melatonin for people who already have dementia, which is about its use in that group.1
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Sources
- National Center for Complementary and Integrative Health. Melatonin: What You Need To Know. Bethesda (MD): National Institutes of Health. Last updated May 2024. Opened 2026-10-07.
- Besag FMC, Vasey MJ, Lao KSJ, Wong ICK. Adverse events associated with melatonin for the treatment of primary or secondary sleep disorders: a systematic review. CNS Drugs. 2019;33(12):1167-1186. Opened 2026-10-11.
- Menczel Schrire Z, Phillips CL, Chapman JL, et al. Safety of higher doses of melatonin in adults: a systematic review and meta-analysis. J Pineal Res. 2022;72(2):e12782. Opened 2026-10-11.
- Andersen LP, Gögenur I, Rosenberg J, Reiter RJ. The Safety of Melatonin in Humans. Clin Drug Investig. 2016;36(3):169-175. Opened 2026-10-07.
This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.