Is Long-Term Use of Melatonin Safe?

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Woman taking melatonin supplement pill before bed

At least 3 million Americans take melatonin supplements to help with sleep problems, such as insomnia and jet lag. Both adults and children use such supplements daily, many on an ongoing basis. But is melatonin safe to use on a long-term basis? What kind of side effects might you experience if you use melatonin regularly?

How Melatonin Supplements Affect Your Body

Melatonin doesn't only come in a supplement you buy at the grocery store. Your body makes its own melatonin, a hormone that helps regulate your sleep-wake cycle. Natural melatonin levels rise at night, when it's dark, making it easier to fall asleep, then fall as daylight approaches, so you can wake up.

However, sometimes melatonin production is disturbed. One cause: using digital devices like cell phones, laptops and tablets right up until bedtime, an all-too-common occurrence today for many of us. Unfortunately, these devices emit a type of light that can turn off or slow down melatonin release, and harm your ability to sleep. Taking melatonin supplements may help correct this problem (though research on effectiveness is mixed).

Other reasons people turn to melatonin supplements include traveling across time zones; working night shifts; having to get up earlier than your body clock likes for work or school; getting older, which may cause melatonin production to decline; and having a medical condition that impairs sleep.

Research shows melatonin supplements can help relieve jet lag and help make it easier for you to wake up earlier (essentially, shifting your body clock–a boon for night owls). It also may improve sleep for elderly people and children, both of whom may have more difficulty producing melatonin on their own.

However, research is mixed about melatonin's benefits for insomnia for most people. The American Academy of Sleep Medicine says there isn't enough scientific evidence to support using melatonin to get to sleep or stay asleep. Research shows that on average, melatonin cuts the amount of time it takes to fall asleep by only about 7 minutes.

Possible Melatonin Supplement Side Effects

Nonetheless, your doctor may suggest you try melatonin on a short-term basis if you are having sleep problems, since for most people it doesn't cause unwelcome side effects and is not habit-forming. This doesn't mean it is side-effect free, though. About 2% of melatonin users experience these melatonin side effects:

  • Daytime drowsiness

Children may notice the same side effects as adults, as well as agitation and bedwetting.

Other, more rare side effects that should be brought to your doctor's attention include:

  • Cognitive issues: confusion, disorientation, and lack of alertness
  • Nightmares
  • Abdominal cramps
  • Feeling chilled
  • Skin irritation

Most of these melatonin side effects go away on their own within a few days, or stop if you quit taking melatonin. Some, particularly daytime drowsiness, may be caused by taking too large of a dose. Cutting back the amount you take may relieve these effects. Also, avoid driving or using machinery after taking melatonin, especially if you aren't sure how it will affect you or if it causes you to be drowsy.

Another cause for melatonin side effects can be medication interactions. Melatonin is known to interfere with certain types of drugs, including:

  • Blood-thinners (anticoagulants) and anti-platelet drugs
  • Anticonvulsants (anti-seizure medication)
  • Contraceptives
  • Immunosuppressants
  • Sedatives and anti-anxiety medications (such as benzodiazepines)
  • Antidepressants, including fluvoxamine and monoamine oxidase inhibitors (MAOIs)

This means people with conditions such as bleeding disorders, epilepsy, diabetes, depression, and autoimmune conditions, as well as those taking birth-control pills, should check with their doctors before starting melatonin.

Long-Term Melatonin Use and Other Safety Concerns

Is indefinite use of melatonin safe? Are there long-term melatonin side effects to be concerned about?

Unfortunately, there has been little research completed that can help provide answers to these questions. In general, melatonin usage has only been deemed safe for up to three months, even though many people take it for much longer.

Experts caution that people with certain conditions should not take melatonin due to lack of research about its impact on them. These conditions include:

  • Pregnancy: Breastfeeding moms also should avoid melatonin.
  • Dementia: People with dementia metabolize melatonin differently, which could result in excessive daytime drowsiness that might result in falls.
  • Restless leg syndrome: Melatonin lowers the amount of much-needed dopamine in sufferers' brains.

Some children take melatonin on a long-term basis for sleeping problems caused by autism, ADHD, anxiety disorders, depression, or other conditions. Sleep is important to health, and melatonin appears to help children with certain disorders sleep better. For example, the American Academy of Pediatrics reports that long-term melatonin use can improve sleep quality in children with autism spectrum disorder. However, some experts worry that long-term use of melatonin in children could interfere with their growth and development, such as by delaying the onset of puberty.

Research also hasn't yet nailed down appropriate melatonin dosages. Very small doses–0.5 milligrams or less – produce levels similar to what your body makes naturally. But oral supplements of 1 to 10 milligrams can bring the levels of melatonin in your blood to 3 to 60 times normal levels.

In the absence of research-supported guidelines, experts advise children should get no more than 3 to 6 milligrams. Recommended starting doses for adults range from .5 to 5 milligrams. The product is available in quantities as large as 10 milligrams. Talk to your doctor to determine the appropriate dosage for you.

In general, experts say to take the least amount of melatonin that is needed to be effective, and to take it for a short time, such as 1 to 2 months. Then reassess your sleep situation. Is the melatonin making any difference? Are you experiencing side effects? Could you try alternatives to improving your sleep, such as avoiding light-emitting devices before bedtime (or using special blue-light filters or glasses to block this light)?

If you are having sleep concerns, discuss these with your physician or healthcare provider, rather than beginning a course of supplements on your own. This way, you can minimize side effects and potentially dangerous drug interactions. You also may find other solutions to your sleep problems than a melatonin supplement.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Nov 4
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