For most adults with insomnia, 1 to 3 milligrams of melatonin taken one to two hours before bedtime is a reasonable starting dose. That’s significantly less than what many over-the-counter products contain, which often come in 5 or 10 mg tablets. Starting low matters because more melatonin doesn’t mean better sleep, and higher doses are more likely to cause side effects like morning grogginess.
Why Lower Doses Work Better
Your body naturally produces melatonin as darkness falls, signaling your brain that it’s time to wind down. A supplement works by mimicking that signal, binding to receptors in brain areas that regulate both deep sleep and dream sleep. The key insight is that this signaling system responds to very small amounts. Taking 0.5 to 3 mg raises your blood levels to something close to what your body produces on its own. Taking 10 mg floods those receptors far beyond natural levels, which doesn’t improve the sleep signal and can leave you feeling drowsy, dizzy, or nauseated the next day.
The NHS recommends 2 mg of a slow-release formulation as the standard adult dose for short-term insomnia, taken one to two hours before bed. For longer-term sleep problems, doctors may gradually increase the dose based on response, but the ceiling is typically 10 mg. Johns Hopkins Medicine suggests 1 to 3 mg taken two hours before bedtime as a practical starting point.
Doses for Older Adults
Most clinical trials in adults over 55 have used 2 mg of prolonged-release melatonin nightly. In three large studies involving people aged 55 to 93, this dose was the standard tested against placebo. The benefits were modest. The American Academy of Sleep Medicine noted only small improvements in sleep quality across these trials, and gave a weak recommendation against using 2 mg melatonin for insomnia in this age group, citing low-quality evidence.
That said, older adults produce less melatonin naturally, which is part of why sleep quality tends to decline with age. If you’re over 60 and considering melatonin, starting at 1 to 2 mg is the most studied approach. Going higher without medical guidance isn’t supported by the evidence.
Doses for Children
Children are more sensitive to melatonin and need much smaller amounts. The American Academy of Pediatrics recommends starting at 0.5 to 1 mg, taken 30 to 90 minutes before bedtime. Most children who respond to melatonin, including those with ADHD, don’t need more than 3 to 6 mg.
Long-term safety in children is less well studied than in adults. There are specific concerns about potential effects on growth and development, particularly around puberty. Short-term use appears relatively safe, but pediatric melatonin use should be guided by a doctor rather than self-directed.
When to Take It
Timing matters as much as dose. Taking melatonin too close to bedtime is a common mistake. The supplement needs time to reach effective levels in your bloodstream. For immediate-release tablets, take them 30 minutes to two hours before you want to fall asleep. Slow-release formulations, which dissolve gradually to keep levels steady through the night, follow a similar window.
If you’re using melatonin for jet lag rather than chronic insomnia, start taking it two hours before your intended bedtime at your destination, beginning a few days before travel.
What the Label Doesn’t Tell You
Melatonin is sold as a dietary supplement in the United States, which means it isn’t held to the same manufacturing standards as prescription medications. A study highlighted by the American Academy of Sleep Medicine found that the actual melatonin content in supplements varied dramatically from what the label claimed. Lot-to-lot variability within a single product differed by as much as 465%. Even more concerning, 26% of tested supplements contained serotonin, a compound that isn’t supposed to be there and is far more tightly regulated.
This means a bottle labeled “3 mg” might contain significantly more or less per tablet. If you’ve tried melatonin before and found it either useless or overwhelming, the dose you actually took may not have been what you thought. Choosing products with third-party testing certifications (look for USP or NSF labels) can reduce this risk.
Common Side Effects
At typical doses, melatonin side effects are generally mild. The most frequently reported include headache, dizziness, nausea, and daytime drowsiness. Less common effects include vivid dreams or nightmares, irritability, stomach cramps, and brief low mood. You should avoid driving or operating machinery for five hours after taking it, since the drowsiness effect can linger.
Higher doses increase the likelihood and intensity of these effects. This is one more reason to start at the lowest dose that works rather than reaching for a 10 mg tablet.
Drug Interactions to Know About
Melatonin interacts with several common medication categories. If you take blood thinners, combining them with melatonin may increase bleeding risk. Blood pressure medications can become less effective, since melatonin itself affects blood pressure. Sedatives and anti-anxiety medications can combine with melatonin’s drowsiness effect, potentially causing excessive sedation. Birth control pills can do the same.
People taking anti-seizure medications should be particularly cautious, as melatonin may reduce their effectiveness and increase seizure frequency. The antidepressant fluvoxamine raises melatonin levels in the body and can cause excessive drowsiness. And because melatonin stimulates immune activity, it can interfere with immunosuppressant drugs used after organ transplants or for autoimmune conditions.
Melatonin’s Limits for Chronic Insomnia
Here’s something most people don’t realize: major sleep medicine organizations don’t actually recommend melatonin for chronic insomnia. The American Academy of Sleep Medicine’s clinical guidelines suggest that clinicians should not use melatonin to treat ongoing insomnia in adults. The evidence simply doesn’t show consistent, meaningful benefits for people who struggle with sleep night after night.
Where melatonin does have stronger support is for circadian rhythm problems, situations where your internal clock is out of sync with when you need to sleep. Jet lag, shift work, and delayed sleep phase (when you naturally fall asleep very late and wake very late) all respond better to melatonin than general insomnia does. If your issue is that you lie awake despite feeling tired, or you wake repeatedly through the night, the problem is likely something melatonin alone won’t fix. Cognitive behavioral therapy for insomnia is considered the first-line treatment for chronic sleep difficulties and addresses the underlying patterns that keep insomnia going.