Melatonin dosing is not based on body weight for adults. Unlike many medications where heavier people need more and lighter people need less, melatonin works as a signaling hormone, not a drug that needs to reach a certain concentration per kilogram of body mass. The standard starting dose for adults is 1 to 3 mg regardless of whether you weigh 120 pounds or 280 pounds.
Why Weight Doesn’t Drive the Dose
Most medications are processed through the bloodstream, where a larger body means more blood volume and more tissue to reach. That’s why weight-based dosing makes sense for painkillers, anesthetics, and antibiotics. Melatonin works differently. It’s a hormone your brain already produces naturally, and supplemental melatonin acts mainly as a timing signal, telling your body’s internal clock that it’s time to prepare for sleep. A small amount is enough to deliver that signal whether you’re petite or large.
What actually determines how much melatonin you need has more to do with your liver enzymes than your scale. Melatonin is broken down primarily by a liver enzyme called CYP1A2. Some people have naturally fast versions of this enzyme and clear melatonin quickly, while others metabolize it slowly. Caffeine intake, smoking, and certain medications can also speed up or slow down this enzyme. Age matters too: older adults tend to produce less melatonin on their own and may metabolize supplements differently than younger adults. These individual differences in metabolism explain why 1 mg knocks one person out while another feels nothing from 3 mg, and none of it has to do with body size.
Recommended Doses for Adults
For short-term insomnia, the typical dose is 1 to 5 mg taken about one to two hours before you want to fall asleep. The NHS recommends starting at 2 mg in a slow-release form, while Poison Control lists 1 to 5 mg as the standard range for insomnia. For jet lag, 3 mg of an immediate-release tablet is standard, with the option to go up to 6 mg if needed, taken for up to five days after a flight.
For longer-term sleep issues, starting at 2 mg and gradually increasing if needed is the usual approach. The maximum recommended dose caps out at around 10 mg per day. Most sleep specialists suggest that if you’re not seeing results at 5 mg, taking more is unlikely to help and may actually make sleep worse by causing grogginess or disrupting your natural sleep cycle the following night.
More Is Not Better
One of the most common mistakes with melatonin is assuming a higher dose will produce deeper or faster sleep. In reality, doses above 3 to 5 mg often lead to side effects without additional benefit. Common issues include daytime drowsiness, headache, dizziness, and nausea. In one reported case, a man who normally took 6 mg increased to 24 mg before a surgery to help himself relax. Within 20 minutes he became lethargic and disoriented, slept for five hours, and woke up appearing “drugged” with no memory of the previous evening.
These side effects aren’t dangerous in the way an overdose of a prescription sleep aid would be, but they defeat the purpose. If you’re waking up groggy or feeling foggy the next day, your dose is likely too high, not too low.
Immediate-Release vs. Slow-Release
The type of melatonin you take can matter as much as the amount. Immediate-release tablets dissolve quickly and create a sharp spike of melatonin in your blood, which is useful for falling asleep faster or resetting your clock after travel. Slow-release (sometimes labeled “extended release”) tablets release melatonin gradually over several hours, mimicking your body’s natural production pattern. This format works better for people who fall asleep fine but wake up in the middle of the night.
Slow-release formulations are typically dosed at 2 mg to start, while immediate-release versions often come in 3 mg or 5 mg tablets. The difference in dosing reflects how each type delivers the hormone, not a difference in potency.
Children and Weight-Based Dosing
Weight-based dosing is sometimes discussed for children, but even in pediatric use there are no universally adopted mg-per-kilogram guidelines. The American Academy of Sleep Medicine advises that parents discuss melatonin with a pediatric healthcare provider before starting it, and that many childhood sleep problems respond better to changes in schedules and habits than to supplements. If melatonin is used for a child, the provider typically recommends a specific dose and timing based on the child’s age and sleep issue rather than a strict weight calculation. The AASM also recommends choosing products with the USP Verified Mark, a third-party quality seal, since only a handful of melatonin products have earned it.
How to Find Your Right Dose
Start with 1 to 2 mg about one to two hours before bedtime. Give it three to five nights before deciding it isn’t working. If you feel nothing, increase by 1 mg at a time rather than jumping to a high dose. If you wake up groggy, try cutting your dose in half or switching from an immediate-release to a slow-release form (or vice versa, depending on your sleep pattern).
Timing often matters more than the milligram count. Taking melatonin too late, say 15 minutes before bed instead of an hour or two, reduces its effectiveness regardless of dose. Taking it too early can make you drowsy before you’re ready for sleep and wear off before morning. Experiment with timing before experimenting with higher doses.