Melatonin is measured in milligrams, not grams, and the difference matters. One gram equals 1,000 milligrams, so even a single gram of melatonin would be 100 times higher than the recommended upper limit. Most adults need between 1 and 5 milligrams, and many people respond well to doses under 1 milligram.
Starting Dose for Adults
The best approach is to start at 1 milligram and increase by 1 milligram each week if you’re still having trouble falling asleep. Many people find that low doses work just as well, or better, than the high-dose tablets (5 mg or 10 mg) commonly sold in stores. For short-term insomnia, 2 mg of a slow-release formulation taken one to two hours before bedtime is a standard recommendation. For longer-term sleep problems, the starting dose is the same, but it can be gradually increased up to a maximum of 10 mg per day if lower doses aren’t effective.
The key point: more is not better with melatonin. Higher doses can actually cause more side effects without improving sleep quality, and excess melatonin in your system can linger into the next day, leaving you groggy.
Why Grams Would Be Dangerous
Adults should not take more than 10 milligrams at a time. To put the gram-versus-milligram difference in perspective, a typical melatonin tablet contains 1 to 5 mg. Taking a full gram (1,000 mg) would be like swallowing 200 of those 5 mg tablets at once. No health authority has established a safe upper limit in the gram range, and there’s no reason anyone would need a dose that high. If you see a product listed in grams, double-check the label carefully for a decimal point or the abbreviation “mg.”
Doses for Jet Lag
For resetting your internal clock after travel, you actually need less melatonin than you might expect. The CDC notes that 0.5 to 1 mg is often enough to produce a circadian shift, and doses above 5 mg are specifically not recommended for jet lag. Higher amounts can linger in your body and end up active at the wrong time of day, which defeats the purpose.
Timing matters more than dose size here. For eastward travel, take melatonin about 90 minutes before your target bedtime to help your body clock shift earlier. For westward travel, taking it when your internal clock thinks it’s morning can help shift your rhythm later. Taking melatonin during the hours when your body is already producing it naturally (roughly midnight to 5 a.m.) is less effective.
When to Take It
For general sleep problems, take melatonin one to two hours before you want to fall asleep. If you’re using a slow-release formulation for ongoing insomnia, 30 minutes to one hour before bed is typical. Swallow slow-release tablets whole rather than crushing or chewing them, since breaking the tablet changes how quickly the melatonin enters your system.
Consistency matters. Taking melatonin at the same time each evening helps reinforce your sleep-wake cycle. Pairing it with other sleep habits, like dimming lights and avoiding screens, makes it more effective than relying on the supplement alone.
Common Side Effects
At recommended doses, melatonin is well tolerated. The most common side effects include headaches, dizziness, nausea, and stomach discomfort. Some people report vivid or strange dreams, night sweats, dry mouth, or feeling irritable. These effects are more likely at higher doses, which is another reason to start low.
Serious side effects are rare, occurring in fewer than 1 in 1,000 people. Signs that warrant prompt medical attention include blurred vision, fainting, confusion, vertigo, unexplained bruising, or blood in your urine. Persistent low mood after starting melatonin can also be a signal to stop and reassess.
Slow-Release vs. Immediate-Release
Most clinical dosing guidelines are based on slow-release (also called extended-release or prolonged-release) tablets. These release melatonin gradually over several hours, mimicking the way your brain naturally produces it throughout the night. They’re designed to help you stay asleep, not just fall asleep.
Immediate-release melatonin hits your bloodstream faster and wears off sooner. It can be useful if your main problem is falling asleep initially, and it’s the form more commonly used for jet lag at lower doses (0.5 to 3 mg). The two forms aren’t interchangeable at the same dose, so it’s worth knowing which type you’re taking when deciding how much to use.