Melatonin: How Many mg for Sleep? 0.5, 1, 3 or 5 mg, and When to Take It

This study best illustrates the principle that with melatonin 'less may be enough'. A dose of 0.3 mg, about ten times smaller than the most popular 3 mg in the shop, restored concentrations close to nocturnal levels and improved sleep efficiency in older people with reduced efficiency. The 3 mg dose also helped, but at the cost of keeping the hormone concentration high into the morning, which in theory may promote morning drowsiness. Important caveats: the trial was small (30 people), concerned older people, and in people without sleep problems melatonin did not work at all.

Here a nuance appears that is worth stating honestly: the meta-regression indicated that higher doses were associated with a somewhat greater effect on falling asleep and sleep time. It does not follow, however, that 5 mg is a good first dose. Meta-regression is an observational analysis comparing different studies (different populations, types of insomnia and durations), not a direct comparison of doses within one trial. At the same time, the same review shows that the total benefit is small, on the order of minutes, even in the best conditions. The practical conclusion is therefore: start with a low dose, assess the effect, and raise it carefully and only if it makes sense.

The time of intake depends on the goal. When you want to fall asleep faster, the standard advice is 30-60 minutes before the planned time of sleep, in a dimmed room; this is also how melatonin was given in the Zhdanova study (30 minutes before bed). When the goal is to shift the circadian rhythm, for example in delayed sleep phase, what matters is not the time relative to sleep but relative to your own melatonin rhythm, measured by the onset of its secretion in dim light (DLMO).

The practical conclusion from this work is interesting: a lower dose (0.5 mg) can produce a similar size of rhythm shift to a 3.0 mg dose, provided it is given at the right moment, and the optimal moment for the lower dose is later. This does not mean, however, that everyone should swallow melatonin in the afternoon: the study concerned healthy young adults in laboratory conditions and rhythm shifting, not the treatment of insomnia. If you suspect a circadian rhythm disorder (e.g. very late falling asleep despite tiredness), talk to a doctor or a sleep specialist instead of searching for the 'ideal hour' yourself; we write more about this syndrome in the entry on delayed sleep phase syndrome.

Immediate-release tablets give a quick peak concentration and stay in the body briefly, so they are associated with help in falling asleep. Prolonged-release (PR) forms lengthen the period during which melatonin is available, with the aim of mimicking the natural secretion profile and for people who find it hard to stay asleep. In Europe a prolonged-release preparation is registered as a medicine, for short-term treatment of primary insomnia in people aged 55 and over.

The result does not suggest that prolonged release is universally better, only that in older people with insomnia it gave a clearer benefit than in younger ones. For most younger adults the evidence of an advantage for the prolonged form is limited. If you are over 55 and insomnia is persistent, the choice of form and dose belongs to the doctor; using a supplement of uncertain composition would be a step in the wrong direction (see below).

This study should change the approach to the 'how many mg' discussion. If the label says 1 mg, the tablet may contain anything from a fraction of that dose to several mg, and differences between lots of the same product can be large. The analysis concerned the North American market and a specific set of products from 2017, so we cannot draw conclusions about Polish preparations from it, but the picture is worrying enough to treat dosing 'to within 0.5 mg' with reserve. In practice: choose preparations with independent confirmation of quality (e.g. a batch-testing certificate), and if possible consider a registered medicine, which is subject to control of its composition.

Melatonin is generally well tolerated, but it is not inert. The most commonly described adverse effects are daytime drowsiness, headache, dizziness, vivid dreams and nausea. The Zhdanova study shows a mechanism that may explain morning heaviness after higher doses: the 3 mg dose caused a fall in body temperature and kept melatonin concentration elevated into daytime hours. So if you feel 'dazed' in the morning, the first step is to lower the dose or take it earlier, not to switch to a stronger preparation.

The melatonin market clearly encourages thinking that 'more is better', and the data say the opposite: physiological doses work, higher ones give no unambiguous advantage, and the effect in all analyses is modest. Add to that the problem of label discrepancies and we have a situation in which the question 'how many mg' is less important than 'what is actually in the tablet and is melatonin a good tool for my problem at all'. We therefore recommend a cautious start from a low dose, choosing a preparation of confirmed quality, keeping to a fixed time, and, for chronic insomnia, reaching for proven non-drug methods.