Your sleep-deprived friends may swear by it and you’ve probably read about it online or seen it on drugstore shelves. But is melatonin all it’s cracked up to be, or are you better off just counting sheep to get some ZZZs?

First, the basics: Melatonin is a naturally occurring hormone in the brain that your body uses to help regulate your circadian rhythm. That’s the 24-hour body clock that, among other vital functions, tells you when to sleep and when to wake up each day.

Your body gradually starts making melatonin about two hours before bedtime, bringing on that familiar drowsy feeling, and production continues throughout the night. In fact, melatonin is often called the “Dracula of hormones” because levels rise when it gets dark outside. As sunrise approaches, levels begin to drop, letting you know it’s time to rise for the day.

Given melatonin’s essential role in the body’s internal clockworks, many people assume the supplement is safe. This may be one reason why it has become the fourth most popular supplement among U.S. adults, according to a National Health Interview Survey. Its use doubled between 2007 and 2012, as more than three million adults reported taking the sleep aid.

And it is true: Melatonin is generally harmless—at least if you take it for a short period of time.

Taking melatonin an hour or two before bedtime can be effective for sleep issues related to your circadian rhythms. There is some evidence that it could be effective for those with temporary jet lag from travelling across time zones, but this research has limitations and the possible benefits appear to be modest.

Shift workers with irregular schedules may also benefit from melatonin use, as may those with delayed sleep-wake phase disorder—a condition that makes it difficult to fall asleep at night, resulting in daytime fatigue. Since melatonin production also declines with age, older people may have trouble falling asleep. In these cases, melatonin may provide some relief, according to Meer Ahmed, MD, of The Sleep Disorder Center at HCA Houston Healthcare West.

But it’s important to talk to your healthcare provider (HCP) before taking melatonin, Dr. Ahmed cautions. Short-term use of melatonin may not be harmful but there is insufficient evidence on its long-term safety, according to the National Center for Complementary and Integrative Health. And in some cases, relying on melatonin could simply mask another problem.

Insomnia is like a fever, Ahmed explains, and is often a symptom of an underlying health concern. For example, sleeplessness could signal a hormonal imbalance, a mental health issue such as anxiety or depression, or a sleep disorder, like sleep apnea. If left untreated, these issues could worsen or possibly lead to complications.

Like all supplements, there are other potential downsides to melatonin use that shouldn’t be overlooked.

It’s important to understand that the U.S. Food and Drug Administration (FDA) doesn’t regulate melatonin or other dietary supplements in the same way that it controls prescription and over-the-counter medications. That means the agency doesn’t test these products for safety or effectiveness, and they could contain harmful hidden ingredients.

A 2017 study published in the Journal of Clinical Sleep Medicine analyzed 31 melatonin supplements and found that the amount of melatonin they contained often varied wildly from what was listed on the label. The hormone serotonin was also detected in 26 percent of the samples analyzed. This could be potentially harmful for some people, particularly those who are taking selective serotonin reuptake inhibitors (SSRIs), antidepressants that increase serotonin levels in the brain. Combining medication or supplements that jointly boost serotonin can cause it to accumulate and reach abnormally high levels in the body—a serious condition called serotonin syndrome, which can result in shivering, diarrhea, muscle rigidity, fever or seizures.

Taking melatonin could also lead to some uncomfortable symptoms. They’re usually mild, but you may experience:

• Nausea
• Dizziness
• Headache
• Sleepiness (when you should be alert)

For these reasons, it’s important to not drive or operate machinery for five hours after taking melatonin.

The supplement could also interfere with other important medications, including blood thinners, diabetes drugs, immune system-suppressing drugs, anti-seizure drugs and some contraceptives. If you’re taking any type of medication, it’s important to talk to your HCP before taking melatonin or any other dietary supplements.

Certain people should be more cautious about melatonin use, particularly if it triggers a negative reaction, including those with:

• Chronic insomnia. Having trouble falling asleep or staying asleep that lasts a month or more shouldn’t be managed with melatonin, according to the American Academy of Sleep Medicine and the American College of Physicians. These groups recommend other more proven remedies (a combination of lifestyle changes, cognitive-behavioral therapy and/or medication), noting that there is not enough evidence that melatonin is safe and effective for long-term use.
• Restless Legs Syndrome (RLS). The tingling or “creepy-crawly” feeling in the legs that often keeps people awake could be worsened by melatonin. The supplement can intensify RLS symptoms because it lowers the amount of dopamine in the brain, according to the Restless Legs Syndrome Foundation. If you’ve been diagnosed with RLS or suspect that you have the condition, talk to your HCP about lifestyle changes or medications that could help.
• Dementia. This progressive cognitive deterioration is often associated with insomnia, which can tax both patients and their caregivers. But melatonin may do more harm than good among those with dementia since the condition causes people to metabolize the supplement more slowly, resulting in daytime drowsiness. In people with moderate or severe dementia, melatonin supplementation may increase the risk of falls, according to 2015 guidelines from the American Academy of Sleep Medicine.

If you’ve been drinking alcohol, it’s also not safe to take melatonin. Both are sedatives and, if taken together, they could cause you to become overly sedated, Ahmed advises.

Melatonin is also not for you if you’re pregnant or breastfeeding. Researchers simply don’t have enough data to know if it’s safe for fetuses or breastfed babies.

Parents desperate for some shuteye may be tempted to give it to their children. There is some evidence that melatonin can help children with attention deficit hyperactivity disorder (ADHD) or autism spectrum disorder (ASD). Circadian rhythm sleep problems are common in those with these conditions.

But the possible side effects of melatonin use in kids also include increased bedwetting or urination as well as agitation. Consult your child’s pediatrician before trying melatonin. It’s worth noting that sleep problems in children can often be eased by creating a regular bedtime routine and sticking to healthy sleep hygiene practices, just like adults.

Quick fixes are often tempting—and unfortunately often too good to be true. Before reaching for melatonin, consider making some simple lifestyle adjustments that can improve your sleep hygiene and help you sleep more soundly. Moves you can try:

• Stick to a sleep schedule. If possible, go to bed at the same time each night, and get up at the same time in the morning.
• Make your bedroom cool and comfortable. Set the room temperature between 60 and 67 degrees Fahrenheit. Make sure it’s dark and quiet.
• Use light to your advantage. Expose yourself to bright light in the morning but avoid it in the evening. This can help keep your circadian rhythms in sync.
• Wind down. As bedtime approaches, read or do something relaxing like taking a warm bath. Avoid using your laptop, phone or tablet because the blue light they emit can interfere with your sleep.
• Don’t stare at the ceiling. If you can’t sleep, get out of bed and do something relaxing until you feel drowsy again.
• Limit caffeine intake. Be sure to avoid caffeinated foods or beverages, including coffee, soda and chocolate, at least four to six hours before going to bed.
• Skip other potential sleep disrupters. Avoid cigarettes, alcohol and heavy meals too close to bedtime.

Medically reviewed in January 2020.

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