Melatonin Side Effects: Grogginess, Headaches, Dreams and Who Should Avoid It

The most common melatonin side effects are headache, dizziness, nausea and sleepiness, and they are usually mild. Some people also notice next-day grogginess or vivid dreams. Short-term use appears to be safe for most adults, but long-term safety has not been well studied, and some people should check with a clinician first. This guide covers each side effect, what higher doses do, and who should be careful.

It is educational, not medical advice.

Key Takeaways

• Common side effects: headache, dizziness, nausea and sleepiness, usually mild (NCCIH: Melatonin).
• Grogginess: melatonin may stay active longer in older adults and cause daytime drowsiness (NCCIH: Melatonin).
• Dreams: nightmares and abnormal dreams show up in safety reports for melatonin, at rates similar to other sleep aids (Ha et al., 2024).
• Higher doses: in trials of 10 mg or more, melatonin caused more drowsiness, headache and dizziness than placebo, with no detectable rise in serious events (Menczel Schrire et al., 2022).
• Check first if you have epilepsy, take a blood thinner, are pregnant or breastfeeding, or care for someone with dementia (NCCIH: Melatonin).

Common Melatonin Side Effects

In adults, the side effects most often reported with melatonin are mild (NCCIH: Melatonin):

• Headache
• Dizziness
• Nausea
• Sleepiness, which can carry into the next morning

There may also be a risk of allergic reactions (NCCIH: Melatonin). If a side effect is bothering you, stop taking it or ask your clinician about a lower dose.

Does Melatonin Make You Groggy the Next Day?

It can. Sleepiness is one of the listed side effects, and melatonin may stay active longer in older people than in younger people, which can cause daytime drowsiness (NCCIH: Melatonin). If you wake up groggy, the timing or the dose may be the reason. How long a dose stays in your system, and how to time it, is covered in how long does melatonin last?

Because melatonin can make you sleepy, do not drive or use machinery until you know how it affects you.

Melatonin and Vivid Dreams

Many people say melatonin gives them vivid or strange dreams. A study of more than 35,000 adverse event reports in the World Health Organization safety database found that nightmares and abnormal dreams were reported more often with melatonin than with medicines in general, but not more often than with other sleep medicines (Ha et al., 2024). The full picture is in our guide does melatonin cause nightmares?

Side Effects at Higher Doses

A systematic review of 79 randomized trials with 3,861 adults looked at melatonin doses of 10 mg or more. In the trials that met its quality bar, melatonin did not cause a detectable rise in serious adverse events or in people dropping out because of side effects, but it did increase milder effects such as drowsiness, headache and dizziness. The authors noted that many trials reported side effects poorly, so the evidence is limited (Menczel Schrire et al., 2022).

Questions about specific doses, such as whether 10 mg or 20 mg is too much, are answered in our melatonin dosage guide.

Is It Safe to Take Melatonin Long Term or Every Night?

Short-term use appears to be safe for most people, but the possible long-term side effects are unclear (NCCIH: Melatonin). A review of studies lasting 6 months or longer found few clinically significant side effects, while warning that there are not enough long placebo-controlled trials to be sure (Besag and Vasey, 2022). For how long people use melatonin and other common sleep aids, see our guide on how long to use sleep supplements.

Whether you can take melatonin every night, how much is too much and whether it is habit forming are covered in our melatonin dosage guide. If you find you need a sleep aid most nights for weeks, talk with a clinician about the cause.

If you mainly use melatonin for travel, our guide to jet lag explains what research shows on timing and dose.

If you are wondering about a drink at dinner, our guide to melatonin and alcohol explains why it is best to skip melatonin on nights you drink. For dose and timing for women at different ages, see melatonin for women.

Who Should Check Before Taking Melatonin

• People with epilepsy and people taking blood thinners should use melatonin only under medical supervision (NCCIH: Melatonin).
• Pregnant or breastfeeding? There is little research on melatonin safety in pregnancy or breastfeeding, so check with your clinician (NCCIH: Melatonin).
• People with dementia: the American Academy of Sleep Medicine recommends against melatonin use in people with dementia (NCCIH: Melatonin).
• Older adults: melatonin may last longer and cause daytime drowsiness (NCCIH: Melatonin).
• Children: give melatonin to a child only with a pediatrician’s advice, and store it out of reach. A CDC report estimated about 11,000 emergency department visits for unsupervised melatonin ingestion by children 5 and under from 2019 to 2022 (NCCIH: Melatonin).
• Taking other medicines? Ask your pharmacist before adding melatonin to any regular prescription.

Check the Label: Melatonin Amounts Vary

Some side effects may come from getting more melatonin than the label says. A 2023 study found that 22 of 25 over-the-counter melatonin gummy products were inaccurately labeled, with contents ranging from 74 to 347 percent of the labeled amount, and a 2017 study found serotonin in 26 percent of the supplements tested (NCCIH: Melatonin).

• Start low. Choose a product that states the exact amount of melatonin per serving.
• Look for third-party tested ingredients.
• Time it well. How to time a dose is covered in how long does melatonin last?

An old bottle adds another unknown, so see does melatonin expire for shelf life and storage.

Our Melatonin Nasal Spray

Our Melatonin Nasal Spray contains 200 mcg (0.2 mg) of melatonin and 17 mg of theanine per two-spray serving, a low amount of melatonin. It is absorbed through the lining of the nose instead of being swallowed. Use it as the label directs, and see our melatonin spray guide for how to use it.

Prefer to skip melatonin? See sleep supplements without melatonin, or compare options in magnesium vs melatonin. More on the hormone itself is on our melatonin ingredient page, and our sleep health guide covers the bigger picture. For melatonin next to 5-HTP, a serotonin precursor, our guide to 5-HTP vs melatonin compares how each is studied for sleep.

Sources

• National Center for Complementary and Integrative Health. Melatonin: What You Need To Know. NCCIH
• Ha M et al. Investigating the safety profiles of exogenous melatonin and associated adverse events: A pharmacovigilance study using WHO-VigiBase. J Pineal Res, 2024. PubMed
• Menczel Schrire Z et al. Safety of higher doses of melatonin in adults: A systematic review and meta-analysis. J Pineal Res, 2022. PubMed
• Besag FMC, Vasey MJ. Adverse events in long-term studies of exogenous melatonin. Expert Opin Drug Saf, 2022. PubMed

Frequently Asked Questions

What are the side effects of melatonin?

The most common are headache, dizziness, nausea and sleepiness, and they are usually mild. Some people also notice next-day grogginess or vivid dreams.

Does melatonin have side effects the next day?

It can cause morning grogginess, especially in older adults, at higher doses or when taken late at night.

Can melatonin cause weird dreams?

Vivid dreams and nightmares are reported with melatonin, at rates similar to other sleep medicines.

Are melatonin side effects worse at higher doses?

Trials of 10 mg or more found more drowsiness, headache and dizziness than placebo, but no detectable rise in serious side effects.

Is it safe to take melatonin long term?

Short-term use appears safe for most people, but long-term safety has not been well studied.

Who should not take melatonin?

Check with a clinician first if you have epilepsy, take a blood thinner, are pregnant or breastfeeding, or have dementia. Give it to children only with a pediatrician’s advice.

Can melatonin cause headaches?

Yes, headache is one of the most commonly reported side effects.

How can I lower the chance of side effects?

Use a low dose, time it well, and choose a product that states the exact amount per serving.

These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before starting a new product if you are pregnant, breastfeeding or taking medication.