Melatonin Supplements: What the Science Actually Says

Melatonin is one of the most widely used sleep supplements in the world, available over the counter in many countries and used by millions of people every night. But the way most people use it is at odds with what the research actually supports.

What Melatonin Does — and Does Not Do

Melatonin is not a sedative. It is a chronobiotic — a hormone that signals to your body that darkness has arrived and it is time to prepare for sleep. Your pineal gland naturally produces melatonin in response to diminishing light, with levels rising in the evening and peaking around 2-4am. Supplemental melatonin works by reinforcing this timing signal, which is why it is most effective for circadian rhythm issues — jet lag, shift work adjustment, and delayed sleep phase syndrome — rather than general insomnia.

The Dosing Problem

Most commercial melatonin supplements contain far more melatonin than the body naturally produces or that research supports. Typical supplements contain 3-10mg, but studies consistently show that doses of 0.3-0.5mg are sufficient to raise blood melatonin to physiological levels and are equally effective for sleep timing. Higher doses can cause next-day grogginess, vivid nightmares, and paradoxically disrupt sleep architecture. They can also desensitise melatonin receptors over time, reducing the supplement's effectiveness. If you use melatonin, start with the lowest dose available and work up only if needed.

Timing Matters More Than Dose

For adjusting sleep timing, melatonin should be taken 2-3 hours before your desired bedtime — not immediately before bed as most people take it. At this earlier timing, it aligns with your natural melatonin rise and strengthens the circadian signal. For jet lag, the timing depends on the direction of travel: take melatonin at your destination's bedtime for eastward travel, and avoid it for the first few days of westward travel where delaying your clock is the goal.

Quality and Regulation Concerns

In the United States, melatonin is classified as a dietary supplement rather than a medication, meaning it is not subject to the same regulatory scrutiny as prescription drugs. A study published in the Journal of Clinical Sleep Medicine tested 31 melatonin supplements and found that the actual melatonin content ranged from 83% less to 478% more than what was stated on the label. Some supplements also contained serotonin, a prescription-controlled substance in many contexts. If you use melatonin, choose pharmaceutical-grade or third-party tested products from reputable manufacturers.

Who Benefits Most From Melatonin

The strongest evidence supports melatonin use for jet lag recovery, delayed sleep-wake phase disorder (common in teenagers and young adults), shift work sleep disorder, and sleep difficulties in older adults whose natural melatonin production has declined. For general insomnia unrelated to circadian issues, cognitive behavioural therapy for insomnia (CBT-I) has consistently outperformed melatonin in clinical trials and is recommended as the first-line treatment by sleep medicine organisations worldwide. Melatonin can be a useful tool, but it works best when used precisely and for the right reasons.