Medically reviewed by Jamie Johnson, RDN

• Melatonin is generally safe, but it can cause side effects if you take it in high doses.
• You may experience sleepiness, dizziness, and an upset stomach if you overdose on melatonin.
• Stop taking melatonin and seek medical care if you’re concerned.

Melatonin is one of the most popular sleep supplements, and for good reason. It can help treat conditions like insomnia and may even benefit people with traumatic brain injuries and migraines.

While melatonin is generally safe and nontoxic, taking more than your body needs can increase the risk of side effects. Although it’s possible to overdose on melatonin, thankfully, life-threatening reactions are extremely rare.

Risks of Taking Too Much Melatonin

You can take melatonin supplements safely in moderate doses—less than 5 milligrams—for short periods.

Taking too much or using it longer than recommended can increase your risk of side effects from melatonin, such as:

• Headache
• Fatigue
• Dizziness
• Upset stomach
• Vivid dreams or nightmares
• Bedwetting (in children)
• Rash
• Fractures (in older adults)

Melatonin overdose can also cause serious symptoms that require urgent medical attention:

• Difficulty breathing
• Seizures
• Chest pain
• Tremors
• Rise in blood pressure

In rare cases, some people may experience allergic reactions or other effects on bodily processes when taking melatonin, such as changes in blood pressure, blood sugar, and seizure threshold (how easily a person may have a seizure). This is why you should consider speaking to a healthcare provider before using this supplement.

Thankfully, melatonin doesn’t last long in the body. It takes about 40-60 minutes for your body to eliminate half of the melatonin you consume. It might take another five hours for melatonin to be 94-97% eliminated from the body. However, certain melatonin formulations, like prolonged-release types, may take longer to be eliminated from the body.

More research is needed to better understand how melatonin can affect you in the long term. Some research suggests that long-term melatonin use may reduce semen quality. It’s best to use melatonin only for a short period, except when otherwise recommended by your healthcare provider.

Medications That May Interfere With Melatonin

Melatonin can also interfere with some medications, such as:

• Blood thinners like Coumadin (warfarin)
• Antidepressants like Luvox (fluvoxamine)
• Antibiotics like Cipro (ciprofloxacin)
• Caffeine
• Oral birth control
• Immunosuppressants (drugs that lower your immune system activity)
• Alcohol
• Other sleep aid supplements, such as kava, valerian, or L-tryptophan

Recommended Dosage

There’s no well-defined standard dose for melatonin. However, various studies have used melatonin doses ranging from 0.1 to 10 milligrams.

Experts consider low to moderate doses of melatonin, between 5 and 6 milligrams, to be safe and effective for daily use. Doses as low as 1 milligram can actually be just as effective as higher amounts and may reduce the risk of overdosing. For best results, melatonin should be taken 30-60 minutes before bedtime. 

The recommended doses for different ages include:

• Infants (under 2): 1 milligram (mg)
• Children (2-9): 2.5-3 mg
• Adolescents (10–17 years): 5 mg
• Adults (18+): 5-6 mg
• Children with special needs: 0.5-10 mg

Some studies have found that taking melatonin at doses above 10 milligrams increases the risk of side effects. The amount of melatonin in each supplement can vary widely, making it easier to take too much. Some supplements may contain up to 478% more melatonin than the amount listed on the label.

This is why it’s best to stick to the dose and brand recommended by your healthcare provider or pharmacist. It’s also important to make sure your melatonin contains safe ingredients and is purchased only from manufacturers that have been third-party tested.

When buying a supplement, make sure the product is independently tested. Unlike medications, supplements are not regulated by the United States Food and Drug Administration (FDA). This means their quality and safety can vary. Independent testing confirms that the supplement contains the ingredients listed on the label and is free from harmful contaminants. Check for seals from reputable organizations such as NSF International, United States Pharmacopeia (USP), or ConsumerLab.

What To Do in Case of Overdose

A melatonin overdose isn’t usually life-threatening. If you suspect symptoms of melatonin overdose, you should stop taking melatonin and seek medical care. Healthcare professionals will determine the severity of your symptoms and advise you on the next step.

If your child or loved one has irregular breathing or loses consciousness after taking melatonin, seek immediate emergency care.

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Kristina Dawson