Melatonin

Melatonin is more reliable as a clock signal than as a universal sleeping pill. In adults, the best-supported uses in this evidence set are jet lag and delayed sleep-wake phase disorder, a pattern in which a person naturally falls asleep much later than desired. Reviews summarized by the National Center for Complementary and Integrative Health suggest fewer jet-lag symptoms, while a small review and a later randomized trial found earlier sleep in people with delayed sleep timing.

That does not mean every adult with insomnia will benefit. In a randomized trial of 170 adults aged 55 and older with primary insomnia, three weeks of 2 mg prolonged-release melatonin improved subjective sleep quality and morning alertness compared with placebo. This is useful evidence for that specific group and formulation, not proof that every melatonin product improves sleep onset or total sleep time.[9][1]

Your brain makes melatonin in response to darkness. The hormone helps coordinate the body’s circadian rhythms, meaning the roughly 24-hour timing system that influences sleep and wakefulness. This biological role is established, but it does not establish that taking a supplement will correct every sleep problem.

For delayed sleep-wake phase disorder, the timing of the dose was part of the intervention. The National Center for Complementary and Integrative Health describes a four-week randomized trial of 307 adults in which melatonin was taken one hour before the desired bedtime alongside a fixed bedtime; participants fell asleep about 34 minutes earlier and reported better early-night sleep and daytime functioning. That example should not be treated as a universal bedtime rule, because the goal was to shift a delayed clock rather than simply produce sedation.[9][5]

There is no single dose that can be confidently recommended for all adult sleep concerns from these studies. The older-adult insomnia trial used 2 mg in a prolonged-release tablet for three weeks. A 2025 meta-analysis in Parkinson’s disease included five randomized trials with 206 participants and found larger sleep-quality effects in studies using more than 4 mg and immediate-release products, while studies using 4 mg or less and prolonged-release products did not show clear improvement. These subgroup findings come from a disease-specific population and should not be used as a dose-finding guide for everyone else.

Formulation can change what a study actually tests. A randomized study of 57 adults awaiting urological surgery used a 7 mg transdermal patch at 11 p.m. on the night before surgery and reported better subjective sleep. That single-night patch study does not establish that a 7 mg oral product works in people with routine sleep-onset concerns, because absorption, setting, timing, and outcome measures were different.[1][2]

Controlled trials do not point in one direction for every outcome. In a crossover trial of 64 adults aged 40 to 80 with advanced glaucoma, 5 mg of oral melatonin taken daily for 30 days did not differ from placebo for sleep quality, total sleep time, awakenings, or other actigraphy measures. Both groups improved on some questionnaires over time, illustrating why a before-and-after improvement is not enough to show that melatonin caused the change.

A systematic review of medicines for postoperative sleep in adults aged 60 and older found that evidence for melatonin was limited and rated overall certainty as low to very low. Another prospectively registered trial, NCT06486064, followed 84 adults with poor sleep for eight weeks but tested a heat-treated probiotic rather than oral melatonin; sleep scores improved over time in both groups, with no significant treatment-by-time difference, even though exploratory biomarker analyses suggested changes in nocturnal melatonin. A biomarker shift is therefore not a substitute for a meaningful improvement in sleep or daytime function.[3][6]

Short studies have generally been reassuring, but they are not a complete safety assessment. The three-week prolonged-release trial in older adults reported few, mostly minor adverse effects and no evidence of rebound insomnia or withdrawal after stopping. The preoperative patch study reported no adverse events, but it lasted only one night and involved a closely monitored hospital setting.

The supplied human evidence does not establish a universal safe dose, medication-interaction rules, or long-term safety across adults. It also includes highly specific settings, such as Parkinson’s disease, glaucoma, surgery, and chemotherapy, whose sleep problems and concurrent care may differ substantially from ordinary sleep-onset concerns. A chemotherapy trial of 40 adults used 6 mg daily for six months, but that treatment-specific setting cannot answer whether melatonin generally improves sleep in adults. Anyone taking prescription medicines or managing a health condition should check with a clinician or pharmacist rather than transferring a dose or timing schedule from one study to another.[1][7]