Melatonin for Sleep: Does It Work, and Is It Safe?

It can work in instances when you want to adjust your biological sleep clock — say, to overcome jet lag after traveling through several time zones or to shift your schedule entirely so you’re going to bed a few hours earlier. 

Melatonin supplements can benefit shift workers who need to sleep during the day, when the body’s melatonin levels are naturally low. That’s when supplementing with melatonin is “actually quite effective,” Covassin says. 

In older adults, it may be able to prolong sleep when taken for an extended period, though more research is needed. A small study from researchers at Brigham and Women’s Hospital in Boston found that when adults ages 55 to 78 took 5 milligrams of melatonin for two weeks, they increased their sleep time by at least 15 minutes, compared with those who took a placebo. 

Is melatonin safe?

Melatonin is generally safe and well-tolerated. But just because it’s available in the U.S. without a prescription and sold alongside multivitamins and probiotics doesn’t mean it’s risk-free. (In many countries it can be purchased only by prescription.)

“We think since it’s available over the counter that it’s harmless, but it may not necessarily be true,” Covassin says. Short-term use of melatonin supplements can come with a list of side effects, especially when taken in high doses, including headaches, dizziness, nausea, fatigue and daytime sleepiness. Vivid dreams and nightmares have also been reported. “These are mild, but they can also affect your daytime function; think about if you have to drive or if you have to operate machinery,” Covassin points out. 

The National Center for Complementary and Integrative Health (NCCIH) at the National Institutes of Health says melatonin may stay active in older adults longer, which could lead to daytime drowsiness. The research center notes that information on long-term safety is lacking.

More serious, albeit rare, reactions have been linked to melatonin supplements, including changes in heart rate and blood pressure, temporary feelings of depression, seizures and confusion or disorientation. Melatonin has been shown to affect glucose tolerance, or the body’s ability to handle sugar.

There are drug interactions to consider, too. Melatonin can increase bleeding risks among people taking anticoagulants and antiplatelet drugs; it can worsen blood pressure in those taking blood pressure medications, and it can stimulate immune function and interfere with immunosuppressive therapy, according to Mayo Clinic.

“So, obviously, this should be taken with caution,” Covassin says. “And that’s my main recommendation. If you are thinking [about taking melatonin] or if you are already taking melatonin, talk with your provider to determine whether it's actually appropriate for you.”

It’s important to know that, as with all dietary supplements in the U.S., federal regulations are less strict for melatonin than they are for over-the-counter medicines and prescription drugs. A 2017 study published in the Journal of Clinical Sleep Medicine found that the contents of the majority of melatonin products didn’t match what was listed on the label — their concentrations ranged, and so did the presence of other ingredients. 

Adding to the evidence, a study published in 2023 in JAMA looked at melatonin quantities in 25 sleep gummy products, often marketed to children, and found that 22 of them contained different amounts of melatonin than what was declared on the label. The actual quantity of melatonin ranged from 74 percent to 347 percent of the labeled amount; only three products had melatonin levels within 10 percent of the declared quantity.

The American Academy of Sleep Medicine offers a tip: When comparing supplement labels, look for the “USP Verified” mark, which indicates that the formulation meets the requirements of the U.S. Pharmacopeial Convention.

What can you do if you have trouble sleeping?

Interested in making adjustments to your sleep schedule? Before you reach for a pill, Neubauer recommends trying natural methods. You can do this by getting outside and staying active during the day. “Just getting light makes your circadian rhythm more robust, and the more active you are in the daytime, the better chance you have of sleeping more at nighttime,” he says. Because light suppresses the production of melatonin, keep levels low at night — this means limiting the use of your phone, tablet, computer and TV an hour or two before bed.

If you have trouble sleeping more generally, talk with a doctor to figure out the cause, Wyatt says. “It’s rare when sleep goes bad just on its own and it’s not because of other things, like the side effects of a different medication or stress or anxiety or depression or a pain disorder that’s insufficiently treated — there are all sorts of things.”

A third of U.S. adults report that they usually get less than the recommended amount of sleep (seven or more hours per night for adults), according to the Centers for Disease Control and Prevention. The good news: There are treatments for insomnia, and a successful one, cognitive behavioral therapy, doesn’t come in pill form.

“We’re starting to realize treating insomnia is not just about getting a better night’s sleep,” Wyatt says. “It’s to significantly reduce risk for some of these negative health outcomes that could come years to decades later.”  

Editor’s note: This article, originally published June 6, 2022, has been updated to reflect new information.