When to take

Short answer

There is no single “right time” that is valid for everyone, because the aim may be to shift the clock earlier, to make falling asleep easier or to reduce jet lag, and the timing studied differs in each. In laboratory studies, the earliest-shifting effect was seen with afternoon intake; in jet lag studies, intake near the target bedtime at the destination was found effective; early intake in the day, however, can cause sleepiness and delayed adaptation. The times below are study and product-information protocols, not personal recommendations. ^{[1] [3]}

Why can timing matter more than dose?

Because melatonin is a hormone that conveys the information “darkness has begun” to the biological clock, its effect varies with the circadian time at which it is taken. This relationship is called the phase response curve. In the study by Burgess and colleagues, 34 healthy adults aged 18–42 (16 men, 18 women) took 0.5 mg melatonin or placebo (double-blind, order varied) at the same time each day for three days within a cycle of dim light (under 150 lux) and darkness. The largest advance shift was seen when 0.5 mg was taken in the afternoon, 2–4 hours before the dim light melatonin onset (DLMO) or 9–11 hours before the midpoint of sleep; the time of the largest delay shift was less distinct and corresponded to shortly after waking. ^[1]

In the same study, the optimal time of intake was later at the low dose, and both doses (0.5 mg and the previously published 3.0 mg curve) produced advance and delay shifts of similar size when given at their own optimal times. The result suggests that the time may be more decisive than the difference in dose. Limits: the study was conducted in a laboratory, in healthy adults, with three days of administration and in dim light; light exposure in daily life is an additional variable. ^[1]

The AASM’s 2015 guideline supports strategically timed melatonin at a second-line level of confidence for delayed sleep-wake phase disorder, non-24-hour sleep-wake rhythm disorder in blind adults and irregular sleep-wake rhythm in children and adolescents with neurological disease; it recommends against melatonin in older people with dementia. ^[7]

At what time was melatonin given in sleep-onset studies?

The study and product protocols for sleep onset do not give a single time:

• Prolonged-release 2 mg product (Europe): The EMA product information states that for primary insomnia at age 55 and over, the tablet is used once daily, 1–2 hours before bedtime and after a meal, for up to 13 weeks. ^[5]
• Study in older people with insomnia (Zhdanova et al.): In 30 people over 50, doses of 0.1, 0.3 and 3.0 mg were each given for one week, 30 minutes before bedtime. ^[6]

The two protocols involve different forms (prolonged-release and immediate-release), different populations and different doses; timing cannot be carried over from one to the other. The relation to meals also varies by product: the EMA says “after a meal” for the prolonged-release product, while the information for the 3 mg tablet licensed in Türkiye states that food is not expected to affect efficacy or safety but that it is recommended not to eat about 2 hours before and 2 hours after taking melatonin. ^{[5] [4]}

How do direction and time matter in jet lag?

In the Cochrane review, in 9 of 10 studies, melatonin taken near the target bedtime at the destination (22:00–24:00) reduced jet lag on flights crossing 5 or more time zones. The benefit increases with the number of time zones crossed and is smaller on westward flights; the review therefore says it may be used especially for eastward flights and for people who have previously experienced jet lag, and if necessary also for those crossing 2–4 time zones. Melatonin taken early in the day can cause sleepiness and delay adaptation to local time. ^[3]

The SmPC (Turkish KÜB) of the 3 mg tablet licensed in Türkiye sets a similar limit: on the grounds that incorrectly timed intake may have an adverse effect on the circadian rhythm or jet lag, the product information excludes intake before 20:00 or after 04:00 at the destination; it states that the first intake is made at bedtime on arrival and that use lasts at most 5–7 days. These are conditions in the information of the licensed product, not a personal time recommendation. ^[4]

These sources give no schedule for when to start in the period before travel or for how many days to take it; this guide does not either. On direction, the Cochrane summary only reports that the benefit is greater on eastward flights and smaller on westward flights; it does not explain the mechanism.

How does evening light affect the timing of melatonin?

In the retrospective analysis by Gooley and colleagues, 116 healthy volunteers aged 18–30 stayed at a clinical research center for at least five days and were exposed in the 8 hours before bedtime to room light (under 200 lux) or dim light (under 3 lux). Room light, compared with dim light, delayed melatonin onset in 99.0% of individuals and shortened melatonin duration by about 90 minutes; exposure to room light at usual sleep times suppressed melatonin by more than 50% in most trials (85%). The authors state that these findings may have potential effects on sleep, body temperature, blood pressure and glucose balance. ^[2]

This study examines not external melatonin intake but a person’s own melatonin secretion; however, it shows that evening light shifts the melatonin clock. The question of how the effect of externally taken melatonin varies with light conditions was not directly tested in these two studies.

Why does “more and later” not work?

When several findings are read together, the assumption that “a higher dose or later intake has more effect” is not supported:

• In the jet lag review, doses above 5 mg gave no additional benefit; intake at the wrong time carried a risk of sleepiness and delayed adaptation. ^[3]
• In the phase-shift study, the optimal time varied with dose; no result emerged in which the high dose was “more effective,” and at the right time both doses produced a similar shift. ^[1]
• In older people with insomnia, 3.0 mg additionally lowered body temperature and kept plasma melatonin elevated into daylight hours; 0.3 mg corrected sleep efficiency. ^[6]

What is known and what is uncertain about timing?

What is known: the effect of melatonin varies with the time it is taken; afternoon intake is associated with advance shifts and post-waking intake with delay shifts (in healthy adults, in the laboratory); in jet lag, intake near the target bedtime was found effective; the wrong time can be ineffective or have the opposite effect; evening light delays a person’s own melatonin secretion.

What remains uncertain (not measured in these studies): how variables such as light exposure in daily life, shift schedule and chronotype change the optimal time for externally taken melatonin; a direct comparison of the timing of prolonged-release and immediate-release forms; determining the optimal time individually in children (timing in children is on a separate page).

Detailed guideMelatonin: overview, status in Türkiye and evidence summary→ Detailed guideMelatonin benefits: which claims are supported?→ Detailed guideMelatonin harms and side effects→ Detailed guideMelatonin in children: evidence, safety and physician decision→

This guide does not recommend personal doses or times; study protocols only describe study conditions.