Most adults get effective results from 0.5 to 5 mg of melatonin, taken 30 minutes to an hour before bedtime. The NHS lists a maximum prescribed dose of 10 mg per day, while the CDC recommends staying at or below 5 mg for most purposes. Starting low, around 0.5 to 1 mg, is the approach most likely to improve your sleep without unnecessary side effects.
Why Lower Doses Often Work Better
Your brain naturally produces melatonin in small amounts each evening as darkness falls. A supplement doesn’t knock you out like a sedative. Instead, it signals your brain’s internal clock that nighttime has arrived, nudging you toward sleepiness. Because this signaling system is sensitive, even half a milligram can be enough to shift your sleep timing.
The CDC specifically notes that 0.5 to 1 mg is “often sufficient to produce a circadian shift.” Taking more than 5 mg can actually backfire: excess melatonin lingers in your system and is still being broken down when your body thinks it’s morning, which can leave you groggy or disrupt your rhythm further. More is not better here. If 1 mg doesn’t help after a week, moving to 3 mg and then 5 mg is a reasonable approach before concluding it doesn’t work for you.
Common Side Effects
At standard doses, melatonin is well tolerated. The most frequently reported side effects include headache, dizziness, nausea, vivid or strange dreams, night sweats, and daytime drowsiness. Arm and leg pain, dry mouth, itchy skin, and feeling restless or irritable also show up occasionally. These tend to be mild and often resolve when you lower the dose.
A systematic review of clinical trials found no increased risk of adverse effects in people taking melatonin compared to placebo at standard doses. At doses above 10 mg per day, minor side effects like drowsiness, headache, and dizziness become more common, but even then, serious adverse events did not increase. That said, higher doses offer no proven additional sleep benefit for most people, so there’s little reason to push beyond 5 mg.
What Your Supplement Actually Contains
This is one of the most important things to know about melatonin. Because it’s sold as a dietary supplement in the U.S., the FDA does not regulate it the way it does prescription drugs. A 2017 study published in the Journal of Clinical Sleep Medicine analyzed 31 melatonin supplements and found that more than 71% did not contain an amount within even 10% of what the label claimed. The actual melatonin inside ranged from 83% less to 478% more than advertised. Lot-to-lot variability within a single brand varied by as much as 465%.
Even more concerning, 26% of the supplements tested contained serotonin, a completely different compound that is far more tightly regulated when used as a medication. This means that if you take a “3 mg” tablet, you could be getting anywhere from half a milligram to over 14 mg, with no way to tell from the packaging. Choosing products that carry a third-party testing seal (USP, NSF, or ConsumerLab) reduces this risk.
Melatonin for Jet Lag
Jet lag is one of the best-supported uses for melatonin, but timing matters more than dose. For eastward travel, take 0.5 to 1 mg about 90 minutes before your target bedtime in the new time zone. This nudges your internal clock forward, helping you adjust faster. For westward travel, taking melatonin when your body still thinks it’s morning can help push your clock in the opposite direction.
Getting the timing wrong can make jet lag worse. Taking melatonin when your body is already producing its own (roughly midnight to 5 a.m. on your home clock) won’t add much benefit. And taking it at the wrong point in your cycle can shift your rhythm in the opposite direction from what you need.
Medications That Interact With Melatonin
Melatonin has several notable drug interactions. If you take blood thinners or anti-clotting medications, adding melatonin may increase your bleeding risk. It can worsen blood pressure control in people already on blood pressure medication. It also adds to the sedative effect of other sleep aids, anti-anxiety drugs, and even hormonal contraceptives.
People on anti-seizure medications should be cautious, as melatonin may reduce their effectiveness. If you take immunosuppressive drugs (common after organ transplants or for autoimmune conditions), melatonin can stimulate immune activity and work against those medications. One antidepressant, fluvoxamine, dramatically increases melatonin levels in the blood, which can cause excessive drowsiness.
Long-Term Use and Dependency
Unlike many prescription sleep medications, melatonin does not appear to cause dependency or tolerance. You are unlikely to need increasing doses over time to get the same effect, and stopping it does not typically cause rebound insomnia. This makes it a relatively low-risk option for ongoing use compared to other sleep aids.
That said, if you find yourself relying on melatonin every night for months, it’s worth examining the underlying cause of your sleep trouble. Poor sleep hygiene, inconsistent schedules, light exposure from screens, caffeine timing, or an undiagnosed sleep disorder like sleep apnea could all be driving the problem. Melatonin works best as a short-term reset tool or a supplement for specific situations like jet lag and shift work, rather than a permanent fix for chronic insomnia.
Finding Your Right Dose
Start with 0.5 to 1 mg, taken 30 to 60 minutes before you want to fall asleep. Give it a few nights before increasing. If that doesn’t help, try 3 mg. Most people do not need more than 5 mg. If 5 mg still isn’t making a difference, taking more is unlikely to solve the problem, and the issue is probably not a melatonin deficit.
Keep the room dark after you take it, since bright light suppresses both your natural melatonin and works against the supplement. Avoid screens or use a red-light filter in the hour before bed. And remember that because supplement labels are unreliable, switching brands can feel like changing your dose entirely, even if the number on the bottle stays the same.