Melatonin is measured in milligrams, not grams, and the right dose is much smaller than most people expect. For adults, a starting dose of 0.5 to 1 mg taken one to two hours before bedtime is effective for most sleep issues. Many over-the-counter products contain 5 or 10 mg per serving, which is far more than what research supports as optimal.
Why the Dose on the Bottle Is Probably Too High
Walk into any pharmacy and you’ll find melatonin gummies and tablets ranging from 3 mg all the way up to 10 mg or more. These doses are well above what your body naturally produces each night. The European Food Safety Authority recommends no more than 0.3 to 1 mg to improve sleep onset, and a systematic review of studies in older adults found that doses above 6 mg showed no significant sleep improvement compared to placebo. More is not better with melatonin. Taking too much can actually backfire: exposure to unnaturally high levels can desensitize your melatonin receptors, potentially making your sleep worse over time.
A good rule of thumb is to start at 0.5 mg and only increase if you see no effect after a few nights. Most adults will find their sweet spot somewhere between 0.5 and 2 mg. The NHS recommends a standard dose of 2 mg (slow-release) for short-term insomnia in adults, taken one to two hours before bed.
When and How to Take It
Timing matters as much as the dose. Melatonin has a short half-life of 20 to 40 minutes, meaning half of it is cleared from your body within that window. For general sleep support, take it one to two hours before your target bedtime. If you’re using it for jet lag, take it 30 minutes before you plan to sleep in the new time zone. For westward travel, taking it in the morning at your destination can help shift your internal clock later.
Melatonin works best as a signal to your brain that it’s time to wind down. It’s not a sedative. If you take it and then scroll your phone under bright lights, you’re fighting against the very signal you just sent.
Doses for Children
There are no official dosing guidelines for children, which makes this tricky for parents. The American Academy of Pediatrics recommends starting with the lowest possible dose, either 0.5 mg or 1 mg, given 30 to 90 minutes before bedtime. Many children respond well to these low amounts. Even kids with ADHD or other conditions that affect sleep rarely need more than 3 to 6 mg. A pediatrician should be involved before giving melatonin to a child, especially for ongoing use.
Doses for Older Adults
As you age, your body produces less melatonin naturally. That might seem like a reason to take more, but the opposite is true. Older adults are more sensitive to supplemental melatonin and more likely to experience side effects at higher doses. Effective doses in studies of older adults ranged from 0.5 to 6 mg, and starting at the low end (0.5 to 1 mg) reduces the risk of next-day grogginess and dizziness. Because older adults are also more likely to be taking other medications, lower doses help minimize interactions.
Side Effects of Taking Too Much
Common side effects include daytime drowsiness, headache, nausea, stomach pain, dizziness, and unusually vivid dreams or night sweats. These are more likely at higher doses. Some people also report limb pain or feeling “off” the next morning in a way that’s different from typical tiredness.
Less common but more serious reactions include blurred vision, vertigo, feelings of depression, and fainting. Allergic reactions are rare but possible. If you notice persistent low mood after starting melatonin, that’s worth paying attention to, as it can be a sign of a depressive response to the supplement.
How Long You Should Use It
Melatonin is designed as a short-term tool. The NHS recommends using it for no longer than 13 weeks for sleep problems in adults. For jet lag, most people only need it for a few days while adjusting to a new time zone. If you’ve been taking melatonin nightly for months and still can’t sleep without it, the underlying issue likely needs a different approach, whether that’s addressing sleep habits, light exposure, stress, or an undiagnosed sleep disorder.
Supplement Labels Aren’t Always Accurate
One complication with melatonin supplements is that the amount on the label doesn’t always match what’s inside. Unlike prescription drugs, supplements in the U.S. aren’t held to the same strict manufacturing tolerances. The FDA requires supplement companies to meet 100 percent of their label claim throughout a product’s shelf life, but enforcement and testing vary. Some independent analyses have found significant discrepancies between what’s advertised and what’s actually in the pill or gummy. This is another reason to start low: if a product labeled 1 mg actually contains more, you still have a margin of safety.