Melatonin can help you fall asleep faster, but the effect is modest. In clinical trials, it shortened the time to fall asleep by about 15 minutes compared to a placebo. That’s meaningful if you’re lying awake for an hour every night, but it’s not a knockout sleep aid. How well it works depends heavily on why you’re struggling to sleep, when you take it, and what dose you use.
How Melatonin Actually Works
Melatonin isn’t a sedative. It’s a timing signal. Your pineal gland, a small structure in your brain, releases melatonin when darkness falls. This surge tells your hypothalamus to start dialing down the systems that keep you alert: body temperature drops, blood pressure lowers, and your retinas become less responsive to light. The result is that gradual drowsy feeling you get in the evening.
When you take melatonin as a supplement, you’re mimicking that natural signal. It tells your brain “it’s nighttime” even if your internal clock hasn’t gotten the message yet. This is why melatonin works best for problems related to circadian timing (your body clock being out of sync) rather than for general-purpose insomnia caused by stress, pain, or anxiety.
Where Melatonin Helps Most
Melatonin’s strongest evidence is for jet lag and delayed sleep phase, where your internal clock is set to the wrong time zone. The CDC notes that your body adapts to westward travel at about 1.5 hours per day and eastward travel at only 1 hour per day. Melatonin can speed that adjustment: taking it when your internal clock thinks it’s early evening shifts your rhythm earlier (useful for eastward travel), while taking it when your body thinks it’s morning shifts your rhythm later (useful for westward travel). Timing matters more than dose here. Taking melatonin at the wrong point in your cycle can actually worsen the misalignment.
For people whose natural sleep window has drifted late, such as night owls who can’t fall asleep until 2 a.m., low-dose melatonin taken several hours before the desired bedtime can gradually pull the sleep window earlier. This is a circadian correction, not sedation.
For general insomnia, the evidence is mixed. Some trials show a statistically significant reduction in the time it takes to fall asleep, while others show no difference from placebo. People with long-term insomnia saw about a 14 to 16 minute improvement in one review, but separate trials in adults with primary insomnia found no benefit at all. If your sleeplessness stems from racing thoughts, chronic pain, or sleep apnea, melatonin is unlikely to solve the problem.
Why It May Work Better for Older Adults
Natural melatonin production drops dramatically with age. People in their 80s produce roughly one-tenth the melatonin that teenagers do. This decline contributes to the fragmented, lighter sleep that many older adults experience. Because their baseline levels are so low, older adults often respond better to supplemental melatonin than younger people whose pineal glands are already producing plenty on their own.
Timing and Dose
Most people take melatonin right before bed, which is too late. For short-term sleep problems, take a slow-release form one to two hours before your intended bedtime. For ongoing use, 30 minutes to one hour before bed is typical. The goal is to have melatonin levels rising as you’re winding down, not peaking after you’ve already been lying in bed for an hour.
Start with 1 mg. Many supplements come in 5 or 10 mg tablets, but more is not better. The CDC specifically recommends against doses above 5 mg because excess melatonin lingers in your system and can still be circulating at the wrong time the next day, which defeats the purpose. For jet lag, doses as low as 0.5 mg are often enough to shift your circadian rhythm. If 1 mg doesn’t help after a week, increase by 1 mg at a time.
Children who benefit from melatonin, particularly those with ADHD or autism, typically need no more than 3 to 6 mg. The American Academy of Pediatrics recommends that parents work with a pediatrician before starting melatonin and only after establishing consistent sleep habits first.
Side Effects
Melatonin is well tolerated in most people. The most common side effects are headache, dizziness, nausea, and daytime drowsiness, the last of which often signals that the dose is too high or taken too late at night. Less commonly, people report vivid dreams or nightmares, irritability, stomach cramps, and brief feelings of low mood. These side effects generally resolve when the dose is lowered or stopped.
Melatonin does interact with several medication categories. It can increase bleeding risk if you take blood thinners, may reduce the effectiveness of anti-seizure medications, and can compound the sedative effects of other central nervous system depressants like benzodiazepines or certain sleep medications. It may also affect blood pressure and diabetes medications. If you take any of these, check with your pharmacist before adding melatonin.
The Label Accuracy Problem
Because melatonin is sold as a dietary supplement in the United States, it isn’t held to the same manufacturing standards as prescription drugs. A 2017 study published by the American Academy of Sleep Medicine found that more than 71% of melatonin supplements contained amounts that were off by more than 10% from what the label claimed. Actual melatonin content ranged from 83% less than advertised to 478% more. Even different batches of the same product varied by as much as 465%. Perhaps most concerning, 26% of the supplements tested contained serotonin, a controlled compound that was not listed on the label.
If you’re going to use melatonin, look for products that carry a USP (United States Pharmacopeia) or NSF International verification seal. These third-party certifications mean the product has been independently tested to confirm that what’s on the label matches what’s in the bottle.
Who Should Skip Melatonin
Melatonin is not a fix for every sleep problem. If you wake frequently during the night but fall asleep fine, it’s unlikely to help. If you sleep poorly because of untreated sleep apnea, restless legs, chronic pain, or anxiety, melatonin addresses none of those root causes. It’s also not designed for long-term nightly use in most people, though extended-release formulations are prescribed for longer periods in some countries. For healthy adults who occasionally struggle with sleep timing, short-term use at low doses is where melatonin has its clearest role.