Melatonin is a sleep-onset signal, not a sedative. This distinction determines everything about how it should be used and why high doses taken at the wrong time do not work well. The hormone is produced by the pineal gland in response to darkness, signaling to the body that night has arrived and sleep should follow. It does not generate the sleep drive itself, that comes from adenosine accumulation over the day. Melatonin tells your clock when to sleep; it does not make you sleepy the way a sedative does.

Understanding this mechanism explains why the 5 mg and 10 mg doses sold in pharmacies are substantially higher than what most research finds necessary, and why timing matters more than dose.

What Dose Is Effective

A 2001 review published in Sleep Medicine Reviews by the circadian researcher Josephine Arendt found that doses as low as 0.1-0.3 mg produce physiological blood melatonin levels comparable to the brain’s natural nighttime peak. Doses of 0.5-1 mg are adequate for most purposes. Doses above 1-3 mg produce supraphysiological melatonin levels that take longer to clear from the body and may cause next-morning grogginess without providing additional sleep benefit.

The typical 5-10 mg tablet found in US pharmacies reflects marketing and supplement regulation conventions, not research-supported dosing. Because melatonin is sold as a supplement in the United States rather than a medication, dosing is not subject to the same regulatory oversight as prescription drugs.

In most countries outside North America, melatonin is a prescription medication available in doses of 0.5-2 mg. This regulatory context reflects the dose range supported by the clinical evidence.

What Timing Does

Melatonin taken too early in the evening can phase-advance the circadian clock, shifting sleep onset and wake time earlier. Taken too close to sleep, it has limited time to work. The general guideline for using melatonin to initiate sleep at the desired time is to take it 30-60 minutes before the target bedtime.

For jet lag, the timing protocol is different: taking melatonin at the target bedtime of the destination time zone, for 3-5 days, helps the circadian clock shift to the new time zone faster. This is one of melatonin’s best-supported uses.

For shift workers, timing depends on the specific shift pattern. The goal is to take melatonin at the desired sleep time in the new schedule, not at a fixed clock time.

What Melatonin Helps With (and What It Does Not)

Supported by evidence:

  • Jet lag: multiple randomized controlled trials show melatonin reduces jet lag severity and duration when taken at the destination bedtime
  • Delayed sleep phase syndrome (DSPS): people who cannot fall asleep until very late and struggle to wake early respond well to low-dose melatonin taken 5-6 hours before the habitual late sleep onset
  • Shift work adaptation: helps realign the circadian clock to the work schedule
  • Sleep initiation in older adults: older adults produce less melatonin and may respond well to supplementation for sleep-onset difficulty

Not well-supported:

  • Chronic insomnia in otherwise healthy adults without a circadian component: melatonin does not produce the sedative effect or sleep architecture improvements seen with medications like eszopiclone or sleep restriction therapy. Meta-analyses on insomnia specifically show modest improvement in sleep onset latency (average 7 minutes faster) that may not be clinically meaningful
  • Staying asleep: melatonin does not address sleep maintenance insomnia (waking in the middle of the night)

Safety and Next-Morning Effects

Melatonin has an excellent safety profile at therapeutic doses. No serious adverse effects have been documented with short or long-term use in adult dosing ranges. The most common side effect is next-morning drowsiness, which is more common at higher doses due to the longer time required to clear supraphysiological melatonin levels.

There are no documented interactions with most medications at standard doses, though it may enhance the sedative effect of other sleep aids or anxiolytics if taken together.

The question of whether long-term nightly melatonin supplementation affects the body’s own melatonin production (downregulation of pineal synthesis) is not clearly answered by the existing literature. This remains a theoretical concern, not an established risk.

Practical Protocol

For general sleep-onset assistance at an appropriate bedtime:

  • Dose: 0.5-1 mg (not 5-10 mg)
  • Timing: 30-60 minutes before target sleep time
  • Avoid bright light after taking the dose

For jet lag (traveling across more than 4 time zones east or west):

  • Start at the destination bedtime, for 3-5 nights
  • 0.5-3 mg works equally well; no benefit from higher doses
  • Take at a consistent time each night in the destination time zone

For sleep-related hormone effects in men, the relationship between sleep quality and testosterone is covered in The Sleep-Testosterone Connection.