Short answer: melatonin is a timing signal, not a sedative. The doses with the best evidence are small — commonly in the 0.5–3 mg range — and when you take it matters more than how much. Higher doses are widely sold and not better supported.
Melatonin is one of the few supplements where the typical retail dose sits far above the amounts that were actually studied, and where taking more can work against you.
What melatonin actually does
Melatonin is a hormone your body releases as light falls, signalling to the circadian system that night has begun. It shifts the timing of the sleep-wake cycle. It is not a sedative and does not work like one.
The practical consequence: melatonin is strongest where the problem is timing — jet lag, shift work, delayed sleep phase — and weakest where the problem is arousal, pain or a racing mind.
Why the retail dose drifted upward
Much of the research used amounts well under 5 mg, and some of the clearest circadian work used fractions of a milligram. Retail products commonly sell 5 or 10 mg because a larger number is easier to market, not because it performed better.
- Higher doses raise the chance of next-morning grogginess.
- Very high doses can produce blood levels far above anything physiological, for many hours.
- Overshooting the timing signal can shift your rhythm the wrong way.
Timing is the variable that matters
For circadian problems, melatonin is generally taken some hours before the target bedtime rather than at the moment you get into bed. Taking it too late can delay rather than advance your rhythm, which is the opposite of the intent.
Who should ask a clinician first
- Anyone taking anticoagulants, immunosuppressants, anticonvulsants or diabetes medication.
- People with autoimmune conditions or epilepsy.
- Anyone pregnant or breastfeeding.
- Children and adolescents — paediatric use should be clinician-led.
Frequently asked questions
Is melatonin a sleeping pill?
No. It is a circadian timing signal. It helps most where the problem is when you sleep rather than whether you can relax.
Why do shops sell 10 mg if the studies used less?
Because a larger number sells better. The evidence does not show higher doses outperform smaller ones, and grogginess becomes more likely.
Can you become dependent on melatonin?
Physical dependence is not the recognised concern. The more common issue is using it to paper over a sleep problem that has a different cause.
Sources
- National Center for Complementary and Integrative Health — Melatonin: What You Need To Know.
Medical disclaimer. This article is general information, not medical advice, and cannot account for your history, medication or symptoms. Speak to a doctor or pharmacist before starting any supplement. Read our full disclaimer.