12 Things That Happen to Your Body When You Take Melatonin

Updated: Mar. 25, 2021

Melatonin supplements are sold over-the-counter as a remedy for insomnia and trouble sleeping. Sleep experts weigh in on how to use melatonin, whether it really works, and if it's safe.

What happens to your body on melatonin

If you toss and turn in bed on most nights because you have trouble sleeping, you’ve probably heard of the natural sleep aid melatonin. It’s a hormone that’s naturally produced by your body that lets you know when it’s time for sleep. But, this sleep aid is also available as a supplement to treat various sleep disorders, like insomnia.

Eager for a cure, many people turn to the much-hyped supplement for better sleep. In the U.S., melatonin is sold over-the-counter and—like all vitamins and supplements—is less strictly regulated by the Food and Drug Administration than prescription drugs. Like any vitamin or supplement, melatonin can have side effects depending on dosage and usage, so proceed with caution (and mention to your doctor that you are using it).

Before you pick up a bottle of melatonin, learn about the effects it can have on the body.

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Melatonin helps control sleep

“Naturally produced internal melatonin does not induce sleep—it is the biochemical signal of darkness and tells the brain that it’s night, and in humans, night is associated with sleep,” says Steven Lockley, PhD, scientific advisor for Lighting Science. Melatonin is released by the body in the hours before bed, helping to regulate our sleep/wake cycle.

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Supplements may regulate circadian rhythms

The theory is that supplementing with melatonin can help people who have trouble falling asleep. However, Lockley says melatonin can also help for people who work at night or have jet lag. “Melatonin can make us sleepy but it is not a very good hypnotic unless you are trying to sleep at the ‘wrong’ circadian phase, such as a shift worker sleeping in the daytime, or trying to sleep at a new time zone after international travel,” Lockley says.

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It doesn’t always work

The science is mixed when it comes to how well melatonin works for general sleep problems. “It is mildly beneficial in the treatment of long-term insomnia or sleep disorders,” says Dave Walker, RPh, pharmacist and medical advisory board member of the non-profit MedShadow Foundation that tracks medications and side effects. But if you’re a night owl with delayed sleep phase disorder, a study in the journal Sleep does show taking melatonin may help you fall asleep at a more normal time.

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It’s not habit-forming

Melatonin is often preferred by medical professionals instead of prescription drugs to treat sleeping problems for several reasons. These supplements are non-habit forming. They also don’t have any withdrawal symptoms, don’t pose a risk of fatal overdose, and don’t need an increased dosage over time. “It has not undergone formal safety review with the FDA, but a meta-review of existing research found it to have a good safety profile,” says Lockley. A 2015 review published in the journal Clinical Drug Investigation suggests using melatonin in the long-term may only lead to mild side effects. Children, adolescents, pregnant women, and those breastfeeding should consult their doctor before taking melatonin. (More on this later.)

12 Things That Happen to Your Body When You Take Melatonin

Melatonin can cause side effects

Those considering melatonin should be aware of some potential side effects. “Melatonin is not without potential side effects including headaches, depression, daytime sleepiness, dizziness, joint pain, stomach cramps, and irritability,” Walker says. Some people have also reported vivid dreams. Although overdoses aren’t life-threatening, those using melatonin still need to be wary: “You should be cautious taking higher doses—20 mg to 30 mg doses may be harmful to adults,” says Walker.

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It can interact with other meds

Melatonin isn’t for everyone. “The supplements can interact with a number of medications, including anticoagulants and antiplatelet drugs, anticonvulsants, contraceptive drugs, diabetes medications, and medications that suppress the immune system (immunosuppressants),” Walker says. In addition, “do not use melatonin if you are pregnant or breastfeeding, or have an autoimmune disorder, a seizure disorder, or depression,” confirms Richard Shane, PhD, sleep expert and creator of the sleep program called Sleep Easy. “Melatonin supplements may also increase blood pressure levels in people taking some hypertension medications.” Experts recommend you avoid the supplement if you’re in the habit of drinking coffee or alcohol in the evening; plus, you shouldn’t drive after taking melatonin. (Check out these 10 medical reasons why you can’t sleep.)

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It may affect children’s development

Sleep issues are common in children, but sorry parents—melatonin is probably not wise for them. “Children should not be given melatonin unless directed by a physician,” Walker says. Lockley agrees: “We do not recommend melatonin for children,” he says. Researchers haven’t extensively tested the hormone in kids; animal research suggests it may affect reproductive development during puberty. Some studies, including a 2015 review in Sleep Medicine Clinics suggest it could help children with developmental disabilities such as autism. But, for most children, the unknown risks outweigh the potential benefits. Parents who want a fix for their children’s sleep troubles should consult a physician.

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You may need a different dose

To avoid negative side effects, take the lowest dose that will work for you. “Generally doses of 0.2 mg to 5 mg are recognized as a starting dose range for melatonin supplements,” Walker says. “I often see people taking 3 to 5 mg daily. If you don’t get results you may increase the dose slowly over a period of days or weeks.” Shane suggests a dosage of 1 to 3mg. But because the FDA doesn’t regulate supplements, different brands may not have the same potency—even if their label says they do, a 2017 study in the Journal of Clinical Sleep Medicine shows. Because of this, you should be conservative in your dosage, especially when first taking it. (Watch out for these 8 common mistakes insomniacs make when going to sleep.)

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It can mess up sleep if taken at the wrong time

Melatonin supplements may not work the way you think they do—you can’t just pop one before bed. “Taking melatonin at bedtime may not work for you at all since melatonin is a sleep-regulating hormone, not a sleeping pill,” Walker says. “It should be taken at a time that will enhance your normal, naturally occurring melatonin levels. These generally increase when nightfall approaches, depending on the season. The usual peak is between 7 p.m. and 9 p.m. for most people. So taking it 30 to 90 minutes before bedtime works for some people. Those with different types of sleep disorders may benefit by taking it two to three hours before bedtime.” (Find out 8 little changes to sleep better in just one day.)

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Different types affect the body similarly

At the drugstore, it can be overwhelming to see the different brands and types of melatonin supplements. “Melatonin is available as tablets, capsules, gummies, chewable tablets, and even mouth sprays. I’m not aware that any form is better than another,” Walker says. But again, “since melatonin is sold as a supplement, it is not FDA-approved or monitored, and there can be wide variation from one manufacturer to another,” he says. “Pick a reliable brand and stick to it if it seems to work for you.” Shane recommends Best Rest by Pure Encapsulations. “It contains melatonin and a combination of other sleep-inducing ingredients,” he says.

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Long-term effects on the body are unknown

Melatonin supplements are safe, but it’s still probably best to only take them until your sleep schedule is back on track. Less is known about long-term safety, according to the National Center for Complementary and Integrative Health. “Melatonin is considered safe to take for short-term use to help control disrupted sleep cycles for a few days, weeks or months,” Walker says. “Its overall effectiveness in long-term use is questionable.” Also, if melatonin doesn’t seem to be working for you, stop taking it. As always, talk to your doctor about any ongoing sleep problems you’re having in order to work out the best solution for you. (Read about 17 strange things during sleep that can happen to your body.)

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How to help your natural melatonin work

Although supplements may help, there are also other (less costly) ways to boost your body’s natural melatonin. “You can increase melatonin production by getting exposure to sunlight in the morning and afternoon,” Shane says. “Blue light from your computer or phone interferes with the brain’s production of melatonin, so stop using computer and phone one hour before bedtime, and stay at least six feet away from your television screen.”

Lockley explains it might not be the level of melatonin itself that needs adjusting; this varies between people. But rather, it’s the duration and timing of its release. “In the hours before sleep, we want to reduce the intensity and the blue-content to help the brain think it’s night and induce sleep,” he says. Turn lights low and follow a relaxing evening routine. In addition, Shane recommends a pre-bedtime snack of foods rich in melatonin, such as goji berries, walnuts, almonds, pineapple, bananas, and oranges. Next, find out 50 easy ways to sleep better.