Quick answer

Take melatonin in the evening, not during the day. Trials gave it close to bedtime, and for jet lag at bedtime at the destination, between 10 pm and midnight. A 2024 analysis of 26 trials suggested about 3 hours before your target bedtime may work better than the usual 30 minutes.^1,2

Key facts

Both of the EU's approved melatonin statements come with the condition that it is taken close to bedtime.³
The schedule most used in practice, according to the 2024 analysis, is 2 mg taken 30 minutes before bed.²
An ordinary tablet reaches its peak in the blood about 50 minutes after you swallow it.⁴
NCCIH says a 2021 review found melatonin may help with jet lag after eastbound and westbound flights.⁵

Evening, not morning

Taken at the wrong time, early in the day, melatonin is liable to cause sleepiness and to delay adjusting to local time.¹

A morning or midday dose sends a night signal at the wrong time. That is why it can leave you sleepy in the day and, after travel, slow the shift to local time.¹

Being exposed to light at night can block the body's own melatonin production.⁶

Bright light late in the evening works against the same signal a supplement adds, so the light around you at night is part of the timing too.⁶

How long before bed

In a 2024 analysis of 26 trials, the time between taking melatonin and going to bed predicted its effect on falling asleep. The authors suggested that about 3 hours before the desired bedtime may work better than the schedule most used in practice, 2 mg taken 30 minutes before bed.²

The suggestion comes from comparing trials that used different schedules, so it points in a direction rather than setting a rule. If you try an earlier dose, keep it in the evening and expect to feel drowsy sooner.²

Timing for jet lag

In the jet lag trials, melatonin was taken close to the target bedtime at the destination, between 10 pm and midnight. The benefit was larger the more time zones were crossed, and smaller after westward flights.¹

The EU's condition for its jet lag statement is to take melatonin close to bedtime on the first day of travel and on the following few days.³

Start on local time. The point is to send the night signal when it is night where you have landed, not when it is night at home.¹

Night shifts

For people who sleep in the daytime after night shifts, NCCIH says the studies have been small or inconclusive. One review of 7 studies with 263 people found about 24 minutes more daytime sleep but no change in the time taken to fall asleep, and rated the evidence low quality.⁶

The next morning

Sleepiness is one of the side effects reported in studies, and in older people melatonin may stay active long enough to cause drowsiness the next day. Do not drive or use machinery while you feel drowsy, and ask a doctor if you take other medicines that make you sleepy.⁶

Questions people ask

Should I take melatonin right before bed?

A common schedule is 2 mg about 30 minutes before bed. A 2024 analysis suggested that an earlier dose, around 3 hours before the bedtime you want, may work better for falling asleep. Either way, take it in the evening rather than the morning.^1,2

When should I take melatonin before a flight?

The jet lag trials did not give it before departure. They gave it close to bedtime at the destination, and the EU's condition starts on the day of travel. Taken at the wrong time of day it can make you sleepy and slow your adjustment.^1,3

Does the timing change with a bigger dose?

The sources here do not give different timing for different doses. What they agree on is the evening: taken early in the day, melatonin is liable to cause daytime sleepiness whatever the amount.¹

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.