Melatonin explained — the sleep hormone and how it works

Melatonin is a hormone produced by the pineal gland in the brain that regulates the sleep-wake cycle. It is often called the 'sleep hormone' because rising melatonin levels signal to the body that it's time to sleep.

How melatonin works

Melatonin production is controlled by light exposure. As darkness falls, the pineal gland increases melatonin production, promoting drowsiness. In the morning, light exposure suppresses melatonin, promoting wakefulness. This is why the hormone is central to the circadian rhythm — the body's internal 24-hour clock.

What disrupts melatonin

• Blue light from screens: particularly disruptive in the evening, suppressing melatonin and delaying sleep
• Irregular sleep schedules: confuse the natural production cycle
• Shift work and jet lag: misalign melatonin with the actual day-night cycle
• Ageing: melatonin production naturally declines with age

Melatonin supplements

In the UK, melatonin is a prescription-only medicine (unlike the US, where it's sold over the counter). It's primarily prescribed for certain sleep disorders and jet lag. Always consult a GP rather than self-medicating.