According to sleep doctors, the layered answer is tied not only to dosage (more on that below), but also to frequency of usage and the underlying reason you’re taking melatonin from the jump. “While melatonin has its place in sleep medicine, it is not the panacea many people think it is,” says clinical psychologist and sleep specialist Shelby Harris, PsyD, author of The Women’s Guide to Overcoming Insomnia. “Particularly in cases of chronic insomnia, the research on melatonin is actually not largely supportive.”
Setting aside its questionable efficacy as a nightly sleep aid, though, melatonin still isn’t quite the neutral option it might seem to be. “While melatonin supplements are available in the U.S. in the same way as over-the-counter dietary or herbal remedies, it’s important to remember that melatonin isn’t an herb. It’s a hormone produced by the body,” says Naima Covassin, PhD, corresponding author on the JAMA study and assistant professor of cardiovascular medicine at Mayo Clinic. And that’s to say, even though it gets a well-earned reputation for being natural, melatonin can still have a potent, lasting effect when you take too much of it over time.
The risks of taking too much melatonin
While much of the reason melatonin has soared in popularity is due to its few acute side effects—it’s not a sedative drug, but instead, a hormonal signal to the brain that it’s time to sleep—it’s still very possible to take too much of a good thing. “The ideal dose of melatonin for an adult ranges from 0.5 to 5 milligrams, and it should be taken 30 minutes to one hour before bedtime,” says behavioral sleep specialist Carleara Weiss, PhD, sleep science advisor for Aeroflow Sleep.
“Doses higher than optimal can lead to dizziness, headaches, and nausea, and some may experience changes in blood pressure, vivid dreams, or nightmares.” —behavioral sleep specialist Carleara Weiss, PhD
According to the JAMA study, no usage greater than 5 milligrams per day was reported prior to 2005—but starting then, the prevalence of people taking more than 5 milligrams daily increased from 0.08 to 0.28 percent in 2018. While that’s still a relatively low number, the trend is concerning for two reasons: There’s evidence of a “ceiling effect,” says Dr. Covassin, where higher doses are not necessarily more effective for improving sleep; and taking too much melatonin increases the potential for side effects, too. “Doses higher than optimal—that is, 5 milligrams at a time—can lead to dizziness, headaches, and nausea, and some people may experience changes in blood pressure, vivid dreams, or nightmares,” says Dr. Weiss.
Separately, taking even the recommended 5-milligram dose of melatonin daily for a prolonged period of time could eventually cause more harm than good. “Excessive increase in melatonin levels following high-dose supplementation may cause our brain receptors to respond less to melatonin—a sort of desensitization—thus allowing us to benefit less and less from it if use is sustained,” says Dr. Covassin.
Though you could avoid all of the above by taking less than 5 milligrams of melatonin at a time and on a short-term basis, that’s easier said than done. “The lack of FDA regulation creates a market where you can inadvertently purchase melatonin at different concentrations higher than the recommendation,” says Dr. Weiss. In fact, a 2017 study published in the Journal of Clinical Sleep Medicine found that the content of more than 70 percent of melatonin supplements varied by as much as 83 percent less to 478 percent more than what was listed on the bottle.
In certain cases, there’s also the potential for counterproductive effects with other drugs. “People taking birth control, corticosteroids, medication to treat high blood pressure, and anticoagulants should avoid using melatonin or discuss with their doctor before taking it,” says Dr. Weiss.
How sleep doctors suggest safely using melatonin supplements
So long as you’re not overdoing the dosage or popping it daily, a melatonin supplement can serve a short-term purpose. “If you find a small dose helps for occasional insomnia, that’s great,” says Dr. Harris, who also recommends its use, in some cases, for jet lag, as a helpful way to nudge the body’s circadian rhythm toward the daylight schedule of your new location.
The same guidance applies if you need to shift your natural sleep pattern so as to not interfere with work or school obligations. “For example, I might suggest a tiny dosage of 0.5 to 1 milligram of melatonin for someone who is a night owl and sleeps a full eight hours, but on a time-delayed schedule,” she says. “I’d have them take it a few hours before bed to slowly shift their body clock to an earlier sleep and wake time.”
But no matter the reason you’re planning to take a melatonin supplement (again, on a short-term basis), the experts recommend paying extra care to the source of that supplement. “Search for companies with a science-based background and supplements inspected by the United States Pharmacopeial Convention, which will often say ‘USP-verified,’” says Dr. Weiss. Another option is to try eating a few walnuts or pistachios after dinner, both of which are natural sources of melatonin in small quantities.
Above all, though, consider that your daytime and nighttime habits can majorly influence your body’s own production of melatonin (and its hormonal opposite, wakefulness-boosting cortisol). The experts’ top tip? Turn down the lights a few hours before your bedtime and limit your blue-light exposure then, too, as your brain’s melatonin faucet runs most efficiently in darkness.
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