Quick answer

Short-term melatonin use appears safe for most adults. Trials of three months or less found no evidence of harm in 651 people, and reported side effects were mild: headache, dizziness, nausea and sleepiness. Long-term safety is unknown, and some groups should ask a doctor first.^1,2

Key facts

A 2016 safety review found only mild side effects in short-term studies, even at very high doses.³
The longer trials in that review reported mild effects comparable to placebo.³
People taking blood thinners need medical supervision to use melatonin, NCCIH says.²
Reports to US poison centers about melatonin in people aged 19 and under rose more than sixfold from 2012 to 2021.²

Side effects reported in studies

Side effects reported in short-term studies in adults were mild: headache, dizziness, nausea and sleepiness.^2,3

There may be a risk of allergic reactions to melatonin supplements.²

Across 17 trials with 651 people, use for three months or less showed no evidence of harm. A 2016 review of animal and human studies reached the same view of short-term use, and found that longer trials reported only mild effects, similar to placebo.^1,3

Taking it every night for months

NCCIH's view is that short-term use appears safe for most people, but there is not yet enough information on long-term use to be sure.²

NCCIH also reports that sleep guidelines from 2017 and 2019 recommended against melatonin for chronic insomnia because the evidence was too weak. If poor sleep goes on for more than a few weeks, see a doctor to find out why.⁴

Who should ask a doctor first

Ask your pharmacist or doctor first

NCCIH says people taking blood thinner medicines need to be under medical supervision when taking melatonin. A Cochrane review noted case reports suggesting that people taking warfarin may come to harm from melatonin, and called for the possible interaction to be studied.^2,5

Reported in studies

People with epilepsy: NCCIH says they need medical supervision to take melatonin²
People with dementia: sleep medicine guidelines from 2015 recommend against melatonin²
Older adults, who may feel drowsy the next day²
Anyone pregnant or breastfeeding, because human studies are lacking^2,3
Anyone taking prescription medicines, including sleeping pills or other drugs that cause drowsiness²

On breastfeeding, NIH's lactation database has no safety data on mothers taking melatonin. It judges short-term evening use of usual doses unlikely to harm a breastfed baby, though some experts advise against it.⁶

Children and teenagers

Reports to US poison control centers about melatonin in people aged 19 and under rose from 8,337 in 2012 to 52,563 in 2021. Most calls were about children 5 and under who took it by accident at home, and most of those exposed had no symptoms, but 4,097 were hospitalized over the 10 years and 287 needed intensive care.²

A CDC report estimated about 11,000 emergency department visits from 2019 to 2022 for children aged 5 and under who swallowed melatonin without supervision. Many of the cases involved flavored products such as gummies.²

Side effects reported in children have usually been mild: drowsiness, more bedwetting or urination in the evening, headache, dizziness and agitation.²

Because melatonin is a hormone, supplements might affect hormonal development in children, including puberty, menstrual cycles and production of the hormone prolactin. NCCIH says this is not known for sure.²

Talk with a health care provider before giving melatonin to a child, and keep every form of it out of reach and sight.²

What else can be in the bottle

Serotonin turned up in 8 of 31 supplements tested in one study. NCCIH notes that serotonin can have harmful effects even at relatively low levels.^2,7

The melatonin dose itself may be off. In a 2023 test of 25 gummies, all but three held more or less than the label said, from 74 to 347 percent of it, and one held none.⁸

Questions people ask

Is it safe to take melatonin every night?

Nightly use for up to about three months has not shown harm in trials, but NCCIH says there is not enough information on long-term use. If you find you need it most nights, talk to a doctor about why you are not sleeping.^1,2

Can you overdose on melatonin?

Serious outcomes are uncommon but have been reported, mostly in children and teenagers. Over 10 years, 4,097 young people were hospitalized after taking melatonin and 287 needed intensive care. Most of the hospitalizations involved teenagers who had taken overdoses on purpose.²

Is melatonin bad for your liver?

LiverTox, NIH's database of liver injury from medicines and supplements, says melatonin has not been implicated in raised liver enzymes or in clinically apparent liver injury.⁹

Is melatonin safe for older adults?

Several of the largest 2 mg trials enrolled people aged 55 and over. Even so, NCCIH says melatonin may stay active longer in older people and cause daytime drowsiness, and guidelines advise against it for people with dementia, so ask a doctor first.^2,10

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.