Melatonin: What It Does and How to Take It

Medically Reviewed by Nayana Ambardekar, MD on March 19, 2024
4 min read

Millions of Americans take melatonin to fall asleep. It’s one of the most used supplements in the U.S. But to get the most from it, it helps to understand how it works and what it can and can’t do for you.

Melatonin is a hormone your brain makes naturally to control your sleep cycle.

The process is tied to the amount of light around you. Your melatonin level usually starts to rise after the sun sets and stays high during the night. It drops in the early morning, which helps you wake up. That quality -- rising at night, disappearing during the day -- gives melatonin its nickname: the Dracula of hormones.

Shorter winter days with limited light can throw off your melatonin production. Your body also makes less of it as you age.

Because melatonin’s job is to signal your body when it’s time to sleep and time to wake, supplements of the hormone can help with certain sleep problems, including:

  • Jet lag
  • Circadian rhythm disorders among blind people
  • Delayed sleep disorder (when you fall asleep and wake later than a normal sleep pattern)
  • Trouble sleeping for shift workers who must rest during daylight hours
  • Sleep-wake cycle issues among children with disabilities

You can buy a melatonin supplement over the counter. There are two forms -- synthetic, or man-made, and natural, which comes from the glands of animals. Stick to the synthetic version. The natural type can have viruses that could make you sick. The product’s label should say which kind it is, but if you’re not sure, ask a pharmacist or a doctor before you take it.

The FDA regulates melatonin the way it does other dietary supplements, such as vitamins. It’s important to know that they’re not held to the same standards as prescription drugs, so there’s no guarantee how well what you buy will work, or if its ingredients match exactly what’s on the label.

You don’t need a big amount of melatonin to see any benefit. Taking more of it doesn’t make it work better or faster. Start with a small dose. If you find you need more, you can slowly take more over time.

When you take it may be even more important than how much you take. The best timing of your dose depends on the sleep issue you’re trying to solve:

  • To deal with jet lag, take it when you arrive at your destination at the time you’d like to go to bed. Some studies have found that taking it as early as 3 days before your trip can help jet lag symptoms. Keep in mind, though, that melatonin is best when you’re traveling east. There’s no evidence that it helps you adjust to westward travel.
  • If you work the night shift, take it at the end of your workday, but never before you drive home.

Light is the switch that controls when your brain makes melatonin. When you take a supplement, take care that you don’t disrupt its effects with artificial light:

  • Avoid your phone and other tech devices that shine brightly in the hours before bed.
  • Turn off overhead lights in the evening.
  • Bright light in the morning can signal it’s time to wake up.

Melatonin may help children with conditions such as autism and ADHD get better sleep, but that’s a decision a pediatrician should approve.

It seems to be pretty safe as a short-term sleep tool, but scientists don’t know a lot about how it might affect kids who take it for a long time. The supplement may also cause side effects, like drowsiness and the need to pee more at night. So always talk to your child’s doctor before you give melatonin.

If you take melatonin at the wrong time, it will throw off your body’s internal clock.

Some people who take it will have side effects, such as:

  • Nausea
  • Dizziness
  • Headache
  • Drowsiness
  • Irritability

You may be tempted to take more melatonin to get sounder sleep, but too high a dose can also cause those side effects, which could disrupt your sleep even more. Don’t try to take more than you need.

You shouldn’t use melatonin if you:

  • Are pregnant
  • Are breastfeeding
  • Have an autoimmune disorder
  • Have a seizure disorder
  • Have depression

Melatonin can affect the way some medications work, including:

  • Anticoagulant and anti-platelet drugs and supplements
  • Some antidepressants
  • Some anticonvulsants
  • Blood pressure drugs
  • Diabetes drugs
  • Contraceptive drugs
  • CNS depressants
  • Diazepam (Valium)

Before you start taking melatonin, ask your doctor how it could affect other medicines you take.