Melatonin for Sleep: What Research Shows and Safety

What melatonin is

Melatonin is a hormone your brain makes in response to darkness. It helps time your circadian rhythm (24-hour internal clock) and sleep, and light at night can block its production. [1] Melatonin supplements are most often made synthetically. [1] This page covers melatonin as a supplement or medicine used for sleep; evidence labels are explained in How to fall asleep faster.

What the research shows

Side effects and safety

• Short-term use appears safe for most people; long-term safety is not established. [1]
• Common effects include daytime sleepiness or tiredness, headache, stomach ache, nausea, dizziness, irritability or restlessness, strange dreams and night sweats. [5] The NHS says not to drive, cycle or use machinery if you feel sleepy or dizzy. [5]
• Older adults: melatonin may stay active longer in older people and cause daytime drowsiness; the AASM (2015) recommends against it for people with dementia. [1]
• The NHS says to tell a doctor or pharmacist before taking melatonin if you have liver or kidney problems or an autoimmune condition. [6]
• Pregnancy and breastfeeding: there has been a lack of research on safety. [1] See Pregnancy and breastfeeding.
• People with epilepsy and those on blood thinners need medical supervision when taking melatonin. [1]
• Possible serious allergic reactions are rare; the NHS lists swelling of lips, mouth or throat, trouble breathing or fainting as reasons to call emergency services. [5]

Medicines and other sleepy products

The NHS lists many medicines that can interact, including antidepressants such as fluvoxamine, benzodiazepines, blood pressure medicines, NSAIDs, estrogens, opiates, warfarin and sleeping tablets such as zolpidem and zopiclone. [7] Do not combine melatonin with herbal remedies that make you sleepy, since that can increase drowsiness. [7] See How interactions work.

Product quality and children

In the US, melatonin is a dietary supplement regulated less strictly than drugs. Some products do not contain what the label says: a 2017 study of 31 products found most did not match the label, and 26 percent contained serotonin. A 2023 study found 22 of 25 gummy products inaccurately labeled, with melatonin from 74 to 347 percent of the labeled amount. [1] See Product quality and contamination and How supplements are regulated.

A CDC report estimated 11,000 emergency department visits from 2019 to 2022 for unsupervised melatonin ingestion by children 5 and younger, often involving flavored products such as gummies; store them out of reach. [1] Talk to a health care provider before giving melatonin to a child. [1] If a child swallows melatonin, see Poisoning: what to do first; in the US, Poison Help is 1-800-222-1222.

US and UK differences

In the UK, the NHS says melatonin is prescription-only, mainly for short-term sleep problems in people 55 and older, and supplements are not authorized for sale there. [8][9] In many other countries it is a drug available only by prescription. [1]

Melatonin versus magnesium

These are different. Melatonin has stronger guideline attention but is not recommended for chronic insomnia; magnesium has little and low-quality research. [2] See Magnesium for sleep and Natural sleep aids compared.

When to get help

If insomnia lasts, see a doctor: CBT-I is the recommended first treatment (CBT-I). [10] Stop and call a doctor if you feel faint, confused, have vision changes or unexplained bleeding. [5]