Publisher Health

Most people think of melatonin as a natural nod-off aid, kind of like chamomile tea in pill form. Even the name of the popular dietary supplement sounds sleepy — that long “o” sound almost makes you yawn mid-word. But melatonin is also a hormone that our brains naturally produce, and hormones, even in minuscule amounts, can have potent effects throughout the body.

“There are some clinical uses for it, but not the way that it’s marketed and used by the vast majority of the general public,” said Jennifer Martin, a psychologist and professor of medicine at the University of California, Los Angeles.

Experts strongly urge people to consult their doctor or a sleep specialist before taking melatonin, in part because the supplement does not address many underlying health problems that may be disrupting sleep. Anxiety can cause insomnia, as can a host of other potentially serious ailments, such as sleep apnea, restless legs syndrome or mood disorders like depression, that may require medical treatment.

Melatonin, however, is relatively inexpensive and readily available at local pharmacies in the United States (in other countries it typically requires a prescription), and many people will go out and buy it on their own. So what’s the best approach to taking melatonin? Here’s what experts had to say.

How does melatonin work?

During the day, the brain’s pea-sized pineal gland remains inactive. A few hours before our natural sleep time, as it starts to get dark outside and the light entering our retina fades, the gland switches on to flood the brain with melatonin.

“Melatonin is sometimes called the ‘hormone of darkness’ or ‘vampire hormone,’” because it comes out at night, said Matthew Walker, a professor of neuroscience and psychology at the University of California, Berkeley, and the author of the book “Why We Sleep.” As levels of melatonin rise, levels of cortisol, the stress hormone, fall. Respiration slows. Soon, our eyelids begin to droop.

Instead of a lights-out trigger, melatonin acts more like a dimmer switch, turning the day functions off and switching night functions on. So taking a melatonin supplement is sort of like taking a dose of sunset, tricking your body into feeling like it’s nighttime. It doesn’t put you to sleep as much as it tells the body that it’s time to sleep.

“It may take several hours,” said Dr. Ilene M. Rosen, a sleep medicine doctor and associate professor of medicine at the Perelman School of Medicine at the University of Pennsylvania, “which is what I think is the misconception about how melatonin is used.”

Melatonin may make you feel a little drowsier when you take it, but it has a bigger impact on regulating the timing of your overall sleep-wake cycle and helping to set the circadian clock, the roughly 24-hour internal timekeeper that tells your body what time of day it is and syncs it with the outside world.

“The impact it has on our sleep depends on the time of day that you take it,” said Dr. Martin, who is also a spokeswoman for the American Academy of Sleep Medicine. “If you took a sleeping pill in the middle of the day, it would make you feel sleepy. If you took melatonin in the middle of the day, it doesn’t really have that effect.”

Hypnotic drugs like Ambien or Benadryl generally cause people to feel sleepy right away, and the sedation effect of those medications “far exceeds that which they obtain from melatonin,” said Dr. Alon Y. Avidan, a professor of neurology and director of the Sleep Disorders Center at U.C.L.A.

How effective is melatonin?

In one analysis published in 2013 in PLOS One, which combined results from 19 studies involving 1,683 men and women, people who took melatonin supplements fell asleep seven minutes faster and increased overall sleep time by eight minutes. That may not sound like much, but there was a lot of individual variation, and researchers found that melatonin also improved overall sleep quality, including people’s ability to wake up feeling refreshed.

But there’s no guarantee that melatonin will work for you.

Dr. Sabra Abbott, an assistant professor of neurology in sleep medicine at Northwestern University Feinberg School of Medicine, said the most common complaint she hears from patients is “I tried melatonin and it didn’t work.” Many also feel hung over or groggy the next morning.

Dr. Martin said that in many studies, melatonin does not work any better than a placebo but added, “One caveat I always like to mention, though, is that placebos work pretty well for insomnia.”

What about dosage?

We naturally make melatonin in our brains, but only in picogram amounts, or one trillionth of a gram, which Dr. Rosen described as “a whiff of it coming out at dusk.” Over-the-counter melatonin supplements come in much higher milligram doses, or a thousandth of a gram. That’s a big difference.

Many experts recommend starting with the smallest available dosage — 0.5 milligrams to 1 milligram, 30 minutes to an hour before bedtime — and seeing how you do from there. If that has no effect, the dose can be gradually increased.

“If you try a dose, stick to it for a few days before you make an adjustment,” Dr. Martin said. “It’s one of those things that may not happen overnight.”

“Keep a close eye on how you feel the next day,” Dr. Abbott said. “Feeling groggy or hung over is a sign that the dose is probably too high.”

Are there side effects?

The good news: In the short term, at least, melatonin is unlikely to do any harm.

“Compared to most other sleeping pills, the side-effect profile is much better,” and it’s not going to be addictive, said Dr. Bhanu Prakash Kolla, an associate professor of psychiatry and a consultant at the Center for Sleep Medicine at the Mayo Clinic. But because melatonin can cause drowsiness, the Mayo Clinic warns that you shouldn’t drive or operate machinery within five hours of taking it.

Does melatonin affect our dreams?

“Far and away, the most common side effect that I have patients report to me is that their dreams just become much more vivid,” Dr. Abbott said. Scientists aren’t sure why that happens.

Dr. Kolla has also seen patients who have nightmares or disruptive dreams, which are also common with sleeping pills. “In that case, you want to try to lower the dose,” he said. “Or, if it’s too problematic, stop.”

How do doctors use melatonin?

Sleep doctors may use melatonin to help patients with circadian rhythm disorders regulate their sleep-wake cycles. For example, during the pandemic, Dr. Avidan said, “we’ve seen those people who become super night owls” unable to fall asleep until 2 or 3 a.m.

Experts also suggest people use a bright light in the mornings to help them wake up, which has “alerting properties and can suppress any remaining melatonin production,” said Dr. Abbott.

Should you take melatonin for jet lag?

Jet lag is a circadian rhythm disorder, albeit a temporary one, so melatonin may help. To alleviate the worst effects, doctors recommend consulting one of several online calculators available, which ask you for your destination and arrival points, your flight time and your normal sleep patterns. Two sites that Dr. Avidan recommends are Jet Lag Rooster or the calculator from Fleet Street Clinic.

“They’re trying to tell you when to take the melatonin so your body knows: ‘Oh, it’s dusk where I’m going,’” Dr. Rosen said, explaining how you can use the supplement before your trip to readjust your body clock.

How do you pick a reliable brand of melatonin?

Like other dietary supplements, melatonin is not regulated by the Food and Drug Administration, which means there may be wide variation among products. A study published in the Journal of Clinical Sleep Medicine found that the content of more than 70 percent of melatonin supplements varied widely from their label claims. The concentration ranged from 83 percent less than the amount listed to 478 percent more.

Dr. Kolla advised looking for a GLP (good laboratory practice) or GMP (good manufacturing practice) label, which refers to federal regulations designed to affirm a product has the advertised quality and purity. “You really don’t know what you’re getting, so you’re trusting the manufacturer,” he said. Melatonin comes in pills, gummies or liquid; the choice comes down to personal preference, he added.

What are alternatives for chronic insomnia?

Sleep doctors strongly urge people with chronic insomnia to seek out cognitive behavioral therapy, a short-term psychological treatment that can help get to the root of the problem.

“If you give melatonin to a patient and you don’t complement it with behavioral therapy for insomnia, you may not necessarily see the effects that you’re looking for,” Dr. Avidan said.

Many common behaviors can also make it harder for us to fall — and stay — asleep, including using our phones near bedtime, which can hamper natural melatonin production. Meditation may help, as can warm showers and cool bedrooms, or giving up caffeine and alcohol.

“There are a lot of other things people could do to help themselves sleep better,” Dr. Martin said. “They’re just harder.”