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Surprising Side Effects of Taking Melatonin Supplements, Says Science

No, they're not all sleep related.
FACT CHECKED BY Olivia Tarantino

Melatonin is a hormone that is produced in the brain. It regulates the body's circadian rhythm, hormones secreted by the endocrine system, and sleep patterns.

Experts may recommend a melatonin supplement for certain conditions like jet lag or insomnia, but those supplements are synthetically made in a laboratory. (For natural sleep-supporting supplements, check out these 5 Absolute Best Foods to Eat For Better Sleep.) Usually, the supplements come in pill form, but they can also be found in a form that you place in the cheek or under your tongue so it gets absorbed quickly into the body.

If you're looking to take melatonin, here are 5 side effects that you may experience. Read on, and for more on how to eat healthy, don't miss 7 Healthiest Foods to Eat Right Now.

1

Helps You Fall Asleep

sleeping
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Some folks have trouble falling asleep at a usual bedtime. Research shows that taking melatonin supplements can help reduce the length of time young adults and kids fall asleep (in those who have trouble falling asleep). It should be noted that this supplement is not regulated by the Food and Drug Administration (FDA) and should only be used in children and adults after speaking with a medical doctor.

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2

Can Cause Daytime Sleepiness 

Woman using a laptop at home stops, her hand to her head.
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If you take melatonin during the day, it can cause sleepiness. This is why when you take it matters. It is advised not to drive or use machinery for 4 to 5 hours after taking the supplement.

3

Can Lead to Gastrointestinal Symptoms

Middle aged woman suffering from abdominal pain while sitting on bed at home
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When taken orally, melatonin has been reported to have side effects like nausea, abdominal cramps, mild abdominal pain, diarrhea, decreased appetite, and/or constipation. Oftentimes these symptoms happen within the first few days of taking the supplement and then subside after a few days.

READ MOREThe Best Supplements for Digestion, According to Dietitians

4

May Cause Migraine Headaches

Man sitting on bed holding his head.
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When taken orally, melatonin has been reported to cause migraine-like headaches or dizziness, especially during the first few days. The symptoms tend to be more common when melatonin is taken in the morning or at high doses (greater than 50mg).

5

Help with Jet Lag

happy young woman in bed with white sheets stretching in front of windows in morning
Shutterstock / Nenad Aksic

Taking 2 to 3 milligrams of melatonin daily when traveling to a different time zone seems to improve alertness and reduce daytime sleepiness in those with jet lag. There is also some evidence that melatonin supplements may help improve other jet lag symptoms including fatigue.

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Toby Amidor, MS, RD, CDN
Toby Amidor is an award winning dietitian and Wall Street Journal best-selling cookbook author who believes healthy and wholesome can also be appetizing and delicious. Read more