Melatonin Side Effects: Common, Long-Term and in Older Adults

Short answer: The most common melatonin side effects are daytime sleepiness, headache, dizziness and nausea, and they are usually mild. Short-term use appears safe for most adults, but long-term safety has not been well studied, and a 2025 preliminary study linked a year or more of use to higher rates of heart failure. Melatonin also interacts with several common medicines, and older adults feel its next-day effects more strongly. Talk with a doctor or pharmacist before using it regularly.

Common melatonin side effects

Mayo Clinic and the NHS list the same handful of common side effects:

• Daytime sleepiness or grogginess, often called a melatonin hangover. Our guide to the melatonin hangover explains why it happens and how to shake it off.
• Headache.
• Dizziness, which matters most for anyone at risk of falls.
• Nausea and stomach upset.

Less common effects include short-lived low mood, irritability, stomach cramps and vivid dreams. Most side effects fade within a few days or when melatonin is stopped.

Why melatonin causes side effects

Your body makes its own melatonin at night as a timing signal for sleep. Supplements usually deliver far more than the body produces, and the extra can still be active the next morning. Taking it late, or after waking in the night, makes this more likely.

In the United States, melatonin is sold as a dietary supplement, so products are not reviewed for strength or purity before they reach the shelf. Mayo Clinic notes that the amount of melatonin in over-the-counter products varies widely, so a new brand can feel noticeably stronger or weaker than the last one.

Melatonin side effects in the elderly

Melatonin is the most popular sleep supplement among older adults, and it is usually gentler than prescription sleeping pills. Three points still deserve attention after 65:

• Next-day drowsiness and dizziness raise the risk of falls, especially on night-time trips to the bathroom.
• Interactions are more likely, because many older adults already take blood thinners, blood pressure or diabetes medicines.
• Dementia: the American Academy of Sleep Medicine recommends against melatonin for sleep problems in people living with dementia.

Our guide to sleeping pills for the elderly compares melatonin with the other sleep aids older adults commonly use.

Long-term side effects of melatonin

The National Center for Complementary and Integrative Health states that short-term use appears safe for most people, but there is not enough information on long-term safety. Melatonin is not habit-forming in the way many sleeping pills are, which is one reason people take it for months or years.

In November 2025, a study presented at the American Heart Association’s Scientific Sessions looked at adults with insomnia. Those who had used melatonin for a year or longer were about 90% more likely to be diagnosed with heart failure, and about 3.5 times more likely to be hospitalized for it, than similar adults who had not. The study had not yet been peer-reviewed, and it shows an association rather than proof that melatonin caused the difference. It is still a good reason to review nightly, long-term use with your doctor rather than continuing on autopilot.

Melatonin interactions to know about

This list covers the main groups, not every medicine. A pharmacist can check your full list in a few minutes.

Who should talk to a doctor first

• People who are pregnant or breastfeeding, since there is little safety research.
• People with epilepsy, an autoimmune condition or depression.
• Anyone taking the medicines in the table above.
• Parents considering melatonin for a child. Ask the pediatrician first. Poison-center calls about children swallowing melatonin have risen sharply, so store gummies like medicine, not candy.

How to lower the risk of side effects

1. Ask your pharmacist about your other medicines and the lowest amount worth trying.
2. Take it at bedtime, not after waking in the night, so it has time to wear off by morning.
3. Skip alcohol on nights you take it.
4. Choose a third-party tested product, such as one carrying a USP Verified mark.
5. Set a review point. If sleep hasn’t improved within a few weeks, stop and look for the cause with your doctor.

If melatonin isn’t right for you

Melatonin works mainly as a timing signal, so it helps most with jet lag and a body clock that runs late, and much less with waking in the night. For long-term insomnia, cognitive behavioral therapy for insomnia (CBT-I) has the strongest evidence and is recommended first by sleep specialists. Our guide to alternatives to melatonin compares the other options, and our guide to herbs for sleep covers valerian, chamomile and more.

A melatonin-free bedtime routine

SleepDeep is a sealed fabric pouch of dry herbs, worn externally at the navel and held by a reusable belt: no melatonin, nothing to swallow and no tea to prepare. In Dr. Wang’s practice records, adults with long-standing sleep complaints reported settling more easily and fewer night-time interruptions during pouch use. These are selected, uncontrolled observations, and individual experience varies; the evidence overview explains them. SleepDeep works alongside your doctor’s care.

To use it well: wear it on clean, intact skin and remove it if irritation appears; keep the pouch sealed (no opening, brewing or heating); and check with the clinician who knows your medicines if you are pregnant, breastfeeding, managing a complex illness or have herbal allergies. Current details and pricing are on the SleepDeep page.

When to see a doctor

See a doctor if side effects don’t fade after you stop melatonin, if you need a sleep aid most nights for more than a few weeks, or if you snore loudly, gasp or stop breathing in your sleep. Seek urgent help for signs of a serious allergic reaction, such as swelling of the face or trouble breathing, or for chest pain, sudden confusion or thoughts of self-harm. In the U.S., call or text 988 for the Suicide & Crisis Lifeline.

Questions about melatonin side effects

Is it safe to take melatonin every night?

Short-term nightly use appears safe for most adults, but long-term safety is not well established. If you have taken it most nights for more than a few weeks, review it with your doctor, who can also look for the cause of the sleep problem.

Can melatonin cause anxiety or depression?

Short-lived low mood and irritability are listed as less common side effects. If your mood drops after starting melatonin, stop it and tell your doctor. If you have depression, ask before using it.

What are the long-term side effects of melatonin?

They are not well studied. A 2025 preliminary study linked a year or more of use in adults with insomnia to higher rates of heart failure, though it showed an association, not cause and effect. Ongoing nightly use is worth reviewing with your doctor.

What happens when you stop taking melatonin?

Melatonin is not considered habit-forming, so most people can stop without withdrawal. Sleep may feel harder for a few nights if the original sleep problem is still there, which is a sign to address that cause. rebound insomnia

Independent sources

National Center for Complementary and Integrative Health: Melatonin · Mayo Clinic: Melatonin side effects · NHS: Side effects of melatonin · American Academy of Sleep Medicine: Insomnia medicine guideline

General education; ask your own doctor before starting any new treatment if you have a health condition.

The routine behind this article

SleepDeep is the Five Essences external herbal pouch matched to this topic — worn on the body, nothing swallowed. One course is six pouches (about 30 days), with a fresh pouch every five days. $199 per course; the reusable belt is $15 if you don’t have one. Every first course is covered by the 90-Day First-Course Satisfaction Guarantee.

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Wellness support, not medical care.