Melatonin for Sleep: How It Works and When It Helps

What melatonin is

Melatonin is a hormone your body produces naturally in the evening as it gets dark. It signals to your brain that it is time to wind down and prepare for sleep, helping to regulate your internal body clock, or circadian rhythm. Light — especially bright or blue-toned light — suppresses melatonin, which is why screens and bright rooms at night can make it harder to feel sleepy.

Melatonin is also available as a supplement or medicine. In some countries it is sold over the counter, while in the UK and much of the EU it is typically a prescription medicine, particularly for older adults and specific situations. Always check the rules and the leaflet where you are.

When melatonin may help

Melatonin is most useful when the problem is with the timing of your sleep rather than sleep in general. Situations where it is often considered include:

• Jet lag, when your body clock is out of sync with a new time zone
• Delayed sleep timing, where you naturally fall asleep and wake very late
• Some shift-work patterns, to help reset the clock
• Certain age-related or medical sleep issues, under medical guidance

It is less likely to help if your insomnia is driven by stress, anxiety, pain or poor sleep habits. In those cases, addressing the underlying cause usually matters more. You can read more in insomnia explained.

How to use it sensibly

If melatonin has been recommended for you, a few principles apply (always follow your prescriber and the leaflet for exact timing and amounts):

• Timing matters more than amount. Melatonin works by shifting your body clock, so taking it at the right time of evening is key.
• Keep the lights low after taking it to support its effect.
• Use it short-term for most situations, rather than indefinitely, unless advised otherwise.
• Combine it with good sleep habits rather than relying on it alone.

Side effects and cautions

Melatonin is generally well tolerated, but some people experience headache, daytime drowsiness, dizziness or vivid dreams. Because it can cause sleepiness, avoid driving or operating machinery until you know how it affects you. It can interact with some medicines, so tell your doctor or pharmacist what else you take. It is not usually recommended in pregnancy or breastfeeding without medical advice.

Habits that boost natural melatonin

You can support your own melatonin production without any supplement:

• Dim the lights and reduce screen time in the hour before bed
• Get plenty of natural daylight in the morning
• Keep a consistent sleep and wake schedule
• Keep your bedroom cool, dark and quiet

When to seek advice

Speak to a doctor or pharmacist if your sleep problems persist for more than a few weeks, if they affect your daily life, or before trying melatonin alongside other medicines or health conditions. Persistent insomnia deserves a proper assessment rather than long-term self-treatment.

You can browse our sleep aids range, read more in insomnia explained, or shop all. Used thoughtfully and at the right time, melatonin can help reset a disrupted body clock — but it works best as part of healthy sleep habits.

General information only — not medical advice. Always read the patient information leaflet and consult a doctor or pharmacist before starting any medication.