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If you have jetlag or sleep problems, chances are someone has told you to take the dietary supplement known as melatonin. It’s a popular over-the-counter sleep aid. But should you?

Before you take melatonin, here’s what you should know.

What Is Melatonin?

Melatonin is a hormone your brain’s pineal gland produces. It’s often called the sleep hormone because your brain produces it in response to darkness.

Melatonin is also available as a synthetic dietary supplement. It comes in liquids, capsules, tablets, gummies, sprays, lozenges, and even chewing gum.

Most melatonin supplements are immediate-release. That means that after you take them, they dissolve quickly into your bloodstream.

There are also timed-release or extended-release melatonin supplements. These dissolve more slowly, to mimic the release of natural melatonin.

How Does Melatonin Work?

Melatonin’s main function is to maintain your body’s circadian rhythm, or internal clock. Your circadian rhythm is what controls your normal sleep-wake cycle.

Your pineal gland releases melatonin at night, when it’s time to fall asleep, and blocks it in the morning, when it’s time to wake up. Melatonin is what makes you feel sleepy at night.

That’s what should happen. But melatonin levels can get out of sync, making it difficult to fall asleep or stay asleep. Several things can disrupt your body’s melatonin levels:

• Blue light from electronics or LED lights close to bedtime.
• Shift work.
• Jet lag.
• Smoking.
• Stress.
• Not enough daylight during the day.
• Aging.

Why Are Melatonin Supplements Used?

Many people take melatonin supplements for insomnia. An analysis of nine sleep studies found that melatonin can help you fall asleep 7 minutes faster. Because of the small benefits, the American Academy of Sleep Medicine (AASM) doesn’t recommend using melatonin to treat insomnia.

And according to the National Center for Complementary and Integrative Health (NCCIH), there’s not enough strong evidence on the effectiveness or safety of using melatonin for chronic insomnia.

However, the American Academy of Family Physicians recommends using timed-release melatonin as a first-line therapy for older adults with insomnia.

Melatonin supplements can potentially help with other conditions. According to NCCIH ongoing research suggests it’s helpful for the following:

• Jet lag.
• Delayed sleep-wake phase disorder (DSWPD).
• Sleep problems in children.
• Anxiety before and after surgery.

The AASM Clinical Guidelines also recommend timed-release melatonin for the following conditions:

• For the treatment of DSWPD.
• For blind adults with non-24-sleep-wake disorder (N24SWD).
• For children and teens with irregular sleep-wake rhythm disorder (ISWRD) and comorbid neurological disorders.

Is Melatonin Safe?

For most adults, short-term use of melatonin is safe, according to the NCCIH. There’s not enough information on the safety of long-term use of melatonin.

What are melatonin side effects?

Most side effects of melatonin are mild. Common melatonin side effects include:

• Headache.
• Dizziness.
• Nausea.
• Drowsiness.

Timed-release melatonin can make you drowsy throughout the day, so use caution when driving or using heavy machinery.

Children taking melatonin can have additional side effects. These include:

• Increased bedwetting or urination at night.
• Agitation or irritability.

Melatonin nightmares

Some people have reported experiencing bad or vivid dreams while on melatonin. But there’s no conclusive evidence that taking melatonin is what causes the nightmares.

Melatonin supplements can increase REM sleep, which is the stage of sleep where you dream the most. So if the melatonin helps you fall into a deeper sleep, you might also experience more dreams — good and bad — than normal.

Safety precautions when taking melatonin

As a supplement, melatonin is not approved by the Food and Drug Administration to prevent or treat any condition. So, there are no standard dosing recommendations. Taking more than 5 mg of melatonin doesn’t work any better but increases your risk of side effects.

People who should avoid or use caution when taking melatonin

You should avoid taking melatonin if:

• You’re on warfarin or other blood thinners. Melatonin can increase the risk of bleeding in those on anticoagulants and antiplatelets.
• You have epilepsy. Melatonin can decrease how well seizure medication works.
• You’re pregnant or breastfeeding. There’s not enough research on the safety of melatonin use in those who are pregnant or breastfeeding.
• You’re trying to conceive. High doses can affect ovulation, making it difficult to get pregnant.
• You’re an elderly person with dementia. The American Academy of Sleep Medicine recommends against using melatonin because the supplement’s side effects are a serious concern in this group of people.

You should use caution when taking melatonin if:

• You’re older. Melatonin stays in your body longer when you’re older and can lead to daytime drowsiness.
• You have high blood pressure or are on blood pressure medication. Melatonin can increase blood pressure.
• You have diabetes or pre-diabetes. Melatonin can increase blood glucose levels.
• You drink caffeine. It can increase the level of melatonin in your body. This can make you drowsy and sedated a lot longer.

Melatonin and children

And while short-term melatonin appears safe for most children, there’s not enough research on melatonin and children. And long-term effects are unknown.

One concern is that because melatonin is a hormone, it may affect your child’s hormonal development, including puberty and menstruation. Before giving melatonin to children, talk their doctor or pediatrician.

Drug and supplement interactions with melatonin

Melatonin supplements can also interact with other medicines and supplements you take. Medication interactions can make one or both of the medications more or less effective or increase their side effects. Some common medications and supplements that interact with timed-release melatonin include:

• Echinacea.
• Fluvoxamine.
• Hormones, such as estrogens or hydroxyprogesterone.
• Ifosfamide.
• PARP inhibitors, such as olaparib.
• Some quinolone antibiotics, such as moxifloxacin.
• Medications that increase sedation, including most antidepressants.

As with any supplement, there can be other concerns related to your health. So before starting any supplement, talk to your doctor to be sure it’s right for you.