Melatonin or magnesium: Can either supplement help you sleep?

Roughly 6% of Americans use over-the-counter supplements or medications in their quest for a good night’s sleep. Two supplements, melatonin and magnesium, have become increasingly popular as sleep aids. Despite anecdotal accounts of their effectiveness — some people swear by them — we have little evidence that they work. And “there’s no study that has compared them, no head-to-head data,” says Dr. John W. Winkelman, a professor of psychiatry at Harvard Medical School and chief of the Sleep Disorders Clinical Research Program in the Department of Psychiatry at Harvard-affiliated Massachusetts General Hospital.

While melatonin and magnesium are readily available in stores, that doesn’t necessarily mean you should try the supplements — or that they’ll relieve your sleep difficulties if you do.

What is the difference between melatonin and magnesium?

Melatonin, a hormone released by the brain’s pineal gland, helps regulate our daily sleep-wake cycle, also known as our circadian rhythm. “Its release in the brain is very sensitive to light,” Dr. Winkelman says. Research suggests that melatonin may also have other roles in the body that are not completely understood.

Magnesium is not a hormone. It is a mineral that is involved in more than 300 metabolic reactions in the body and which affects a variety of physiological processes, including sleep regulation.

How do melatonin and magnesium work for sleep?

Melatonin and magnesium affect sleep in different ways.

Melatonin promotes a type of relaxation your body needs for sleep. Levels of the hormone rise in response to darkness, and then fall early in the morning so we can wake up.

Small studies suggest that melatonin supplements can help people who have difficulty falling asleep at bedtime and waking up in the morning (delayed sleep-wake phase disorder). Taking the hormone also appears to relieve jet lag.

Magnesium’s effect on sleep is not well understood, but it may be through its regulation of gamma-aminobutyric acid, or GABA, a neurotransmitter that can help calm the nervous system. It also may affect blood levels of both melatonin and cortisol, a stress hormone.

Which is better for falling and staying asleep?

Some evidence, such as a 2022 analysis of studies in Neuroscience and Biobehavioral Reviews, suggests that melatonin may help reduce the time it takes to fall asleep in people who have insomnia.

We don’t have that kind of research for magnesium. Despite social media influencers touting the perks of taking the mineral to fall asleep, clinical studies have not shown a consistent benefit.

And there’s no solid proof to suggest that either supplement can help people stay asleep once they’ve dozed off.

What are the side effects of melatonin vs. magnesium?

“Melatonin is generally not going to produce side effects,” Dr. Winkelman says, provided you don’t take more than 5 to 6 milligrams (mg); an optimal dose hasn’t been established. If you do, “sometimes people have bad dreams or, strangely enough, a hangover or grogginess the next morning,” he says.

Other potential melatonin side effects include

• irritability
• restlessness
• headache
• anxiety
• digestive problems such as nausea and constipation.

Magnesium also can have side effects if you take a dose above 350 mg for adults. Magnesium side effects, when you take too much, include diarrhea, nausea, and abdominal cramping. Extremely high intakes can lead to irregular heartbeat and cardiac arrest.

Is melatonin or magnesium safe for long-term use?

Magnesium appears to be safe for long-term use, provided you stay within safe dosage limits and your kidneys are healthy. Kidneys remove excess magnesium from your body; if they aren’t working properly, extra amounts of the mineral can cause an unhealthy buildup.

The safety of long-term melatonin use hasn’t been adequately studied. The hormone is generally considered safe in low doses taken in the short term.

Who should avoid melatonin?

Melatonin is not generally recommended if you are pregnant or breastfeeding, or if you have a bleeding disorder, depression, or seizures.

The hormone can alter the effectiveness of many medications, including

• blood thinners
• anticonvulsants
• blood pressure drugs
• central nervous system depressants
• diabetes medications
• contraceptives
• immunosuppressants.

If you take one of these drugs, speak with your doctor before taking melatonin.

Who should avoid magnesium?

People with severe kidney disease, heart block, or myasthenia gravis should avoid magnesium supplements.

People taking certain medications also should avoid magnesium. The mineral can interact with

• antibiotics
• gabapentin
• diuretics
• thyroid hormone
• bisphosphonates.

When should you talk to a doctor or pharmacist?

Before you take a sleep supplement, Dr. Winkelman advises discussing your sleep problem with your health care provider to an underlying cause.

Medications, health conditions, and stress can all cause sleep issues. Your clinician can also review your medical history and determine whether any medications you take could interact with melatonin or magnesium.

Should you take melatonin or magnesium for sleep?

Although the supplements are popular, the American Academy of Sleep Medicine does not recommend using melatonin for recurrent or ongoing insomnia. It has no suggestion regarding the use of magnesium.

“Given the fact that we’ve got a lot of well-tested, effective medications [for sleep], I rarely recommend melatonin, and I never recommend magnesium,” Dr. Winkelman says. “Even before we prescribe medications, we’ve got a first-line treatment for insomnia: cognitive behavioral therapy for insomnia, or CBT-i.” CBT-i combines cognitive interventions (reducing anxious thoughts when trying to sleep) and behavioral changes (such as reducing time spent in bed, keeping stable bedtimes and wake times, and cutting back on caffeine and alcohol).

How much melatonin or magnesium should you take?

If it’s warranted — for instance, if you have jet lag from a trip — Dr. Winkelman recommends taking 1 to 3 mg of melatonin (which is many times higher than the 0.3 mg we produce naturally) about an hour before bedtime. Older individuals might want to stick with 2 mg — the amount used in many studies of older people with insomnia — or even less, since our bodies tend to metabolize drugs more slowly as we age.

If it’s warranted, perhaps for a deficiency, a safe starting dose of magnesium is 100 to 200 mg per day, swallowed one to two hours before bed. Doses higher than 350 mg per day can cause side effects. Most types of available magnesium supplements haven’t been studied for sleep, but magnesium glycinate is well absorbed and easy on your stomach.

What should you look for in a sleep supplement?

Look for products that display a seal from U.S. Pharmacopeia or NSF. These independent testing organizations can give you some assurance about quality. That’s important because over-the-counter supplements aren’t evaluated by the FDA, meaning we don’t know exactly what’s in them.

An example of why quality assurance matters: A 2017 study found that the melatonin content of 31 supplements purchased at pharmacies and grocery stores differed, sometimes widely, from the amount listed on the label. And a 2023 Harvard study found that 22 of 25 brands of melatonin gummies had higher or lower doses than listed on their labels; one brand contained more than three times the labeled dose of melatonin.

Speak with your doctor to make sure the sleep supplement is safe to take with other medications or supplements you are already taking.

Frequently asked questions

Is melatonin or magnesium better for anxiety-related sleep issues?

“Most people who have had insomnia for a while develop anxiety about their insomnia,” Dr. Winkelman says. “You get so anxious about the insomnia itself that it’s self-fulfilling — it perpetuates the problem. That makes it very difficult to distinguish insomnia disorder from anxiety-related insomnia.” For that reason, he doesn’t recommend either melatonin or magnesium for anxiety-related sleep issues. Instead, he recommends CBT-i and medications that are shown to be effective for anxiety disorders.

Is melatonin better than magnesium for jet lag?

We don’t have any studies comparing melatonin versus magnesium for jet lag. But melatonin has been found to reduce jet lag, especially after eastbound flights. Taken in the morning (for travel westward), melatonin adjusts the internal clock to a later time; taken in the evening (for travel eastward), it resets it to an earlier time.

Which works faster for sleep?

Because of melatonin’s direct link with the sleep-wake cycle, it can work quickly to improve sleep, while the timeline for magnesium hasn’t yet been determined (studies that found a possible benefit ranged from five days to eight weeks).

Can you take melatonin and magnesium together?

Yes, it’s possible to take melatonin and magnesium together safely because they work differently in the body, but whether the combination can improve sleep hasn’t been established.

Which is better for older adults?

Dr. Winkelman says that research doesn’t support either supplement as a solution for sleep problems in older adults. Study results for melatonin are inconsistent, and the hormone may remain active longer in older people, resulting in daytime drowsiness, fatigue upon awakening, and more sleep disruption. Studies of magnesium’s sleep benefits in older adults have produced mixed results.

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