Melatonin

Melatonin is a hormone produced by the pineal gland in darkness. Its role is not to sedate you but to tell the body that night has begun: it is a timing signal, and the clock reads it rather than obeys it.

That distinction explains why it works well for some problems and poorly for others. Taken in a small dose several hours before your intended bedtime, it can shift the body clock earlier, which is genuinely useful for jet lag, shift work and delayed sleep phase. Taken as a large dose at bedtime, it is a weak sleeping tablet.

Light suppresses it, and evening light is the modern reason it arrives late. Bright light in the hours before bed delays release; morning light advances the whole rhythm the following night. Managing light is a bigger lever than supplementing.

Availability differs by country in ways worth knowing. In the UK melatonin is prescription only and licensed mainly for short term use in adults over 55; in the United States it is sold as a supplement, often in doses ten or twenty times higher than the physiological amount, and analyses of commercial products have repeatedly found actual content differing substantially from the label.

More is not better with it. Doses far above physiological levels do not shift the clock more effectively and are more likely to leave people groggy the following morning.

It is not a solution for insomnia, which has a first line treatment with far better evidence in cognitive behavioural therapy for insomnia. Using melatonin to paper over chronic insomnia, or over a schedule that simply does not allow enough sleep, delays fixing the actual problem.

In practice, treat it as a timing tool used deliberately, fix light exposure first, and take persistent insomnia to a GP rather than to a bottle.