For most adults, anything above 10 mg of melatonin in a single dose is considered too much. The standard therapeutic range is 2 to 5 mg, and many sleep specialists recommend starting at the lowest effective dose, which for most people is between 1 and 3 mg. Higher doses don’t necessarily produce better sleep and are more likely to cause side effects.
Standard Doses for Adults
For short-term insomnia, a typical starting dose is 2 mg of slow-release melatonin taken one to two hours before bed. For longer-term sleep problems, the dose can be gradually increased, but the NHS caps the recommended maximum at 10 mg per day. For jet lag, 3 mg is standard, with up to 6 mg if needed.
These numbers matter because melatonin works differently from most sleep aids. It doesn’t sedate you directly. It signals your brain that it’s time for sleep. Taking more doesn’t amplify that signal in a useful way. In fact, flooding your system with high doses can disrupt your sleep cycle rather than support it, leaving you groggy the next day or waking you up in the middle of the night.
What Happens When You Take Too Much
The most common symptoms of taking too much melatonin are sleepiness that lingers into the next day, headache, nausea, and sometimes agitation or irritability. These effects are uncomfortable but rarely dangerous in adults. There is no established lethal dose for melatonin in humans, and fatal overdoses in adults have not been documented.
That said, “not lethal” doesn’t mean “harmless.” Consistently high doses can cause daytime drowsiness that affects your ability to drive or concentrate. Some people report vivid or disturbing dreams. Others experience dizziness or mild drops in body temperature, since melatonin plays a role in thermoregulation.
The Label Problem
One complicating factor is that you may not be taking the dose you think you are. A study analyzing 31 melatonin supplements found that more than 71% of products didn’t contain the amount listed on the label, even within a 10% margin of error. The actual melatonin content ranged from 83% less to 478% more than what the label claimed. Lot-to-lot variability within a single product was as high as 465%.
This means a bottle labeled “5 mg” could contain anywhere from less than 1 mg to nearly 24 mg per tablet. If you’ve ever felt that melatonin “stopped working” or suddenly hit you much harder than usual, inconsistent manufacturing could be the reason. Melatonin is sold as a dietary supplement in the U.S. and isn’t subject to the same quality controls as prescription medications.
Melatonin and Children
The stakes are higher for kids. Between 2019 and 2022, melatonin was responsible for roughly 11,000 emergency department visits among infants and children aged five and under in the United States. That accounts for about 7% of all ER visits for unsupervised medication exposure in that age group. Poison control calls for pediatric melatonin ingestions surged 530% between 2012 and 2021, driven largely by the growing number of gummy and chewable melatonin products in households.
Most of these cases resolved without lasting harm. Among all pediatric melatonin ingestions reported to poison control during that period, about 1.6% resulted in more serious outcomes. However, five children required mechanical ventilation, and two children under age two died. Investigators couldn’t definitively confirm whether melatonin alone caused those deaths or whether underlying health conditions played a role, but the cases underscore a real risk. If you keep melatonin in your home and have young children, store it out of reach the same way you would any other medication.
Interactions With Other Medications
Taking melatonin alongside certain medications can amplify side effects even at normal doses. The most important interaction to know about is with blood thinners like warfarin, where melatonin can affect how the drug works. Melatonin can also increase the sedating effects of other medications, including antihistamines, benzodiazepines, and other sleep aids. If you’re combining melatonin with anything that makes you drowsy, the combined effect can be stronger than either one alone.
How to Find Your Right Dose
Start with the smallest dose available, ideally 1 mg or less, and take it one to two hours before you want to fall asleep. If that doesn’t work after a few nights, increase by 1 mg at a time. Most people find their sweet spot between 1 and 5 mg. If you’re not seeing any benefit at 5 mg, taking more is unlikely to help, and the issue is probably something melatonin can’t fix, like stress, screen exposure, or an underlying sleep disorder.
Timing matters more than dose. Melatonin taken too close to bedtime, or too early in the evening, won’t align with your body’s natural sleep signals. For general insomnia, one to two hours before bed works for most people. For jet lag, take it at the bedtime of your destination time zone.
If you’ve been taking high doses (10 mg or more) for a long time, you can taper down. Your body produces its own melatonin naturally, typically in amounts well under 1 mg. Supplemental doses of 5 or 10 mg are already many times higher than what your brain releases on its own, which is part of why less often works better.