For most adults, taking melatonin for short-term sleep issues is considered safe. It’s one of the most popular supplements in the world, and health authorities generally agree that brief use at low doses carries minimal risk. The picture gets murkier with long-term use, higher doses, and use in children, where the evidence is thinner and the concerns are more specific.
What Melatonin Actually Does
Your brain already makes melatonin every night. A small gland in your brain produces it after dark, using serotonin as a building block, and this nightly surge is what tells your body it’s time to sleep. The cycle is tightly linked to light exposure: darkness triggers production, and light shuts it down.
When you take a melatonin supplement, you’re adding to that natural signal. Your body reads supplemental melatonin the same way it reads darkness. This is why melatonin is particularly useful for situations where your internal clock is out of sync with your schedule, like jet lag or shift work, rather than as a heavy sedative that knocks you out.
How Much to Take
Less than you probably think. Research on jet lag has found that a dose as small as 0.5 mg can be just as effective as 5 mg or higher for resetting your sleep timing. Most over-the-counter supplements start at 3 to 10 mg, which is already well above what your body produces naturally.
The NHS recommends 2 mg as a standard adult dose for insomnia, taken one to two hours before bed. For jet lag, 3 mg taken 30 minutes before your intended bedtime in the new time zone is typical, used for up to five days. If you’re flying west and need to push your sleep schedule later, taking melatonin in the morning at your destination can help shift your clock in that direction.
Starting low makes sense. You can always increase the dose if a smaller amount doesn’t help, but many people take far more than they need because the supplements come in large doses by default.
Common Side Effects
The most frequently reported side effects are mild: headache, dizziness, nausea, and daytime drowsiness. Some people experience vivid dreams or nightmares, short-lived feelings of depression, irritability, or stomach cramps. These tend to be more common at higher doses.
Because melatonin can cause drowsiness that lingers into the next day, avoid driving or operating machinery within five hours of taking it. Drinking alcohol while using melatonin compounds the sedative effect and should be avoided.
Long-Term Use Is Less Clear
Short-term melatonin use appears safe for most people. Long-term safety, though, hasn’t been well studied. The National Center for Complementary and Integrative Health notes that at doses higher than what the body normally produces, there simply isn’t enough data yet to draw firm conclusions about years of nightly use.
This doesn’t mean long-term use is dangerous. It means the research hasn’t kept pace with how widely and how long people actually take it. If you’ve been using melatonin nightly for months or years, it’s worth revisiting whether you still need it and whether the underlying sleep problem could be addressed differently.
Medications That Can Interact
Melatonin isn’t as benign to combine with other medications as many people assume. It interacts with several common drug classes:
- Blood thinners. Melatonin may increase the risk of bleeding when combined with anticoagulant or anti-platelet drugs.
- Blood pressure medications. Melatonin can worsen blood pressure control in people already on these drugs.
- Seizure medications. Melatonin may reduce the effectiveness of anticonvulsants, potentially increasing seizure frequency.
- Sedatives and CNS depressants. The drowsiness effects stack, which can become excessive.
- Birth control pills. Hormonal contraceptives combined with melatonin may increase sedation and amplify melatonin’s side effects.
- Immunosuppressants. Melatonin can influence immune function, which may interfere with these drugs.
- Fluvoxamine (used for OCD). This medication raises melatonin levels significantly, potentially causing unwanted excessive drowsiness.
If you take any prescription medication, checking for interactions before adding melatonin is important, even though it’s sold over the counter.
The Label Accuracy Problem
One of the less obvious risks of melatonin supplements has nothing to do with melatonin itself. Because supplements aren’t regulated the same way prescription drugs are, what’s on the label doesn’t always match what’s in the bottle.
An FDA study published in 2025 analyzed 110 melatonin supplements marketed for children, all purchased in 2023. The actual doses ranged from 0% to 667% of the amount printed on the label. That means some products contained no melatonin at all, while others had more than six times the stated dose. This kind of variability makes it difficult to control what you’re actually taking, especially for children where dosing precision matters most. Choosing products that carry a third-party testing seal (like USP or NSF) can reduce this risk.
Melatonin and Children
Melatonin use in children has surged in recent years, and this is where caution is most warranted. A systematic review published in The Lancet’s eClinicalMedicine found that melatonin doesn’t appear to cause serious adverse events in children, but it does increase the likelihood of minor side effects compared to placebo, roughly 1.5 times the rate.
The more nuanced concern is hormonal. Melatonin levels naturally decline in children as they approach puberty, and this decline is part of what triggers puberty’s onset. Studies tracking children on melatonin for two to four years found little or no effect on pubertal development. However, one study looking at treatment lasting longer than seven years registered a potential delay in puberty. The worry is that sustained supplemental melatonin could interfere with the gradual hormonal shift that kicks off adolescent development.
For children with genuine sleep disorders, particularly those with ADHD or autism where sleep problems are common and severe, melatonin can be a reasonable tool. But the combination of unreliable supplement dosing and potential hormonal effects means it deserves more careful consideration than a casual nightly gummy.
Who Benefits Most
Melatonin works best when the problem is timing rather than an inability to sleep. Jet lag is its strongest use case. If you’ve crossed multiple time zones and your body thinks it’s 3 PM when it’s actually midnight, melatonin helps compress the adjustment period. It’s also useful for shift workers whose schedules force them to sleep during daylight hours, since melatonin mimics the darkness signal their brain isn’t getting.
For garden-variety insomnia, the effects are more modest. Melatonin typically helps people fall asleep a bit faster, but it’s not a powerful sedative and won’t keep you asleep through the night if that’s your problem. People who expect it to work like a sleeping pill are often disappointed. Behavioral changes, like keeping a consistent wake time, limiting screen light in the evening, and keeping your bedroom cool, tend to have a bigger and more durable effect on chronic insomnia than melatonin alone.