Is melatonin safe to take every night?

Melatonin caused only mild side effects in trials lasting up to a few months, and nightly use for years hasn't been tested well enough to call it proven safe.

Who it's for

Adults using it short term; long-term safety is unknown for everyone.

What to expect

Mild side effects like sleepiness or headache in short trials; sleep gains were small.

Watch out for

Supplement labels often don't match what's in the bottle.

What guidelines say

The National Center for Complementary and Integrative Health says short-term studies in adults reported only mild side effects, but long-term safety information is lacking1Guideline · 2023Melatonin: What You Need To KnowShort-term studies in adults reported only mild side effects, but information on long-term safety is lacking. In tests of supplements, the amount of melatonin in most products didn't match the label.National Center for Complementary and Integrative Health (NIH). It also notes that in most tested products the melatonin amount didn't match the label1Guideline · 2023Melatonin: What You Need To KnowShort-term studies in adults reported only mild side effects, but information on long-term safety is lacking. In tests of supplements, the amount of melatonin in most products didn't match the label.National Center for Complementary and Integrative Health (NIH). The FDA label on one product says to stop use and ask a doctor if symptoms last more than 5 days, and to ask a health professional first if pregnant or breast-feeding12Guideline · 2018Melatonin: FDA drug label (prescribing information)Warnings: WARNINGS Stop use and ask doctor if symptoms persist more than 5 days. If pregnant or breast-feeding ask a health professional before use. Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center right away. Contains ethyl alcohol 30%US Food and Drug Administration.

What the studies show

• A review of 37 placeboplacebo A dummy treatment that looks like the real one, so people can't tell which they got.-controlled trials used daily doses of 0.15 to 12 mg and followed people for up to 29 weeks, though most lasted 4 weeks or less. The most common side effects were daytime sleepiness (about 1.7% of reports), headache, dizziness and sleep-related problems (each under 1%). Serious problems were very rare, and most side effects faded within days or when treatment stopped2Systematic review · 2019Adverse Events Associated with Melatonin for the Treatment of Primary or Secondary Sleep Disorders: A Systematic Review.Few, generally mild to moderate, AEs were associated with exogenous melatonin. No AEs that were life threatening or of major clinical significance were identified. The scarcity of evidence from long-term RCTs, however, limits the conclusions regarding the safety of continuous melatonin therapy over extended periods.…CNS Drugs.
• The same review says too few long trials exist to judge continuous use over long periods, or to judge risk in vulnerable groups. Many trials were of fair or poor quality2Systematic review · 2019Adverse Events Associated with Melatonin for the Treatment of Primary or Secondary Sleep Disorders: A Systematic Review.Few, generally mild to moderate, AEs were associated with exogenous melatonin. No AEs that were life threatening or of major clinical significance were identified. The scarcity of evidence from long-term RCTs, however, limits the conclusions regarding the safety of continuous melatonin therapy over extended periods.…CNS Drugs.
• A review of 17 trials with 651 people found no evidence of harm with use of three months or less4Meta-analysis · 2006 · 651 peopleEfficacy and safety of exogenous melatonin for secondary sleep disorders and sleep disorders accompanying sleep restriction: meta-analysis.There is no evidence that melatonin is effective in treating secondary sleep disorders or sleep disorders accompanying sleep restriction, such as jet lag and shiftwork disorder. There is evidence that melatonin is safe with short term use.BMJ. A review of primary sleep disorders reached the same conclusion for short-term use6Meta-analysis · 2005 · 12 peopleThe efficacy and safety of exogenous melatonin for primary sleep disorders. A meta-analysis.There is evidence to suggest that melatonin is not effective in treating most primary sleep disorders with short-term use (4 weeks or less); however, additional large-scale RCTs are needed before firm conclusions can be drawn. There is some evidence to suggest that melatonin is effective in treating delayed sleep…J Gen Intern Med.
• A trial of 189 older care-home residents, 87% with dementia, gave 2.5 mg of melatonin in the evening for 15 months on average (up to 3.5 years). Melatonin worsened mood scores and increased withdrawn behavior, though not when given with bright light7Randomized trial · 2008Effect of bright light and melatonin on cognitive and noncognitive function in elderly residents of group care facilities: a randomized controlled trial.Light has a modest benefit in improving some cognitive and noncognitive symptoms of dementia. To counteract the adverse effect of melatonin on mood, it is recommended only in combination with light.JAMA. These residents were much older and sicker than most users.
• A 28-day trial of 40 volunteers given 10 mg found no harmful changes in blood tests, hormones or organ markers5Randomized trial · 2000 · 40 peopleRandomized, double-blind clinical trial, controlled with placebo, of the toxicology of chronic melatonin treatment.No other differences between the placebo and melatonin groups were obtained. In the present study we did not observe, according to the parameters analyzed, any toxicological effect that might compromise the use of melatonin at a dose of 10 mg for the period of time utilized in this study.J Pineal Res.
• A review of 19 trials found melatonin's sleep effects did not fade with longer use. This hints at no tolerance, but it doesn't measure long-term safety3Meta-analysis · 2013 · 1,683 peopleMeta-analysis: melatonin for the treatment of primary sleep disorders.This meta-analysis demonstrates that melatonin decreases sleep onset latency, increases total sleep time and improves overall sleep quality. The effects of melatonin on sleep are modest but do not appear to dissipate with continued melatonin use. Although the absolute benefit of melatonin compared to placebo is…PLoS One.

Key studies

Safety

Reported side effects include daytime sleepiness, headache, dizziness and, less often, agitation, mood swings, nightmares and palpitations2Systematic review · 2019Adverse Events Associated with Melatonin for the Treatment of Primary or Secondary Sleep Disorders: A Systematic Review.Few, generally mild to moderate, AEs were associated with exogenous melatonin. No AEs that were life threatening or of major clinical significance were identified. The scarcity of evidence from long-term RCTs, however, limits the conclusions regarding the safety of continuous melatonin therapy over extended periods.…CNS Drugs. A trial in people with migraine found weight loss on 3 mg9Randomized trial · 2016 · 196 peopleRandomised clinical trial comparing melatonin 3 mg, amitriptyline 25 mg and placebo for migraine prevention.Melatonin 3 mg is better than placebo for migraine prevention, more tolerable than amitriptyline and as effective as amitriptyline 25 mg.J Neurol Neurosurg Psychiatry. Pregnant or breast-feeding women should ask a health professional first, and children should not take it without advice12Guideline · 2018Melatonin: FDA drug label (prescribing information)Warnings: WARNINGS Stop use and ask doctor if symptoms persist more than 5 days. If pregnant or breast-feeding ask a health professional before use. Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center right away. Contains ethyl alcohol 30%US Food and Drug Administration. Product contents vary from the label1Guideline · 2023Melatonin: What You Need To KnowShort-term studies in adults reported only mild side effects, but information on long-term safety is lacking. In tests of supplements, the amount of melatonin in most products didn't match the label.National Center for Complementary and Integrative Health (NIH).

What we don't know

• Whether years of nightly use cause rare or late harms, since few people were followed long term1Guideline · 2023Melatonin: What You Need To KnowShort-term studies in adults reported only mild side effects, but information on long-term safety is lacking. In tests of supplements, the amount of melatonin in most products didn't match the label.National Center for Complementary and Integrative Health (NIH),2Systematic review · 2019Adverse Events Associated with Melatonin for the Treatment of Primary or Secondary Sleep Disorders: A Systematic Review.Few, generally mild to moderate, AEs were associated with exogenous melatonin. No AEs that were life threatening or of major clinical significance were identified. The scarcity of evidence from long-term RCTs, however, limits the conclusions regarding the safety of continuous melatonin therapy over extended periods.…CNS Drugs.
• Whether risks differ in older people with dementia, children or other at-risk groups2Systematic review · 2019Adverse Events Associated with Melatonin for the Treatment of Primary or Secondary Sleep Disorders: A Systematic Review.Few, generally mild to moderate, AEs were associated with exogenous melatonin. No AEs that were life threatening or of major clinical significance were identified. The scarcity of evidence from long-term RCTs, however, limits the conclusions regarding the safety of continuous melatonin therapy over extended periods.…CNS Drugs,7Randomized trial · 2008Effect of bright light and melatonin on cognitive and noncognitive function in elderly residents of group care facilities: a randomized controlled trial.Light has a modest benefit in improving some cognitive and noncognitive symptoms of dementia. To counteract the adverse effect of melatonin on mood, it is recommended only in combination with light.JAMA.