What is melatonin?
Melatonin is a hormone produced by the pineal gland in response to darkness. It signals to the body that it is time to sleep by lowering core body temperature and inducing drowsiness. Production is suppressed by light exposure, particularly blue light wavelengths. As a supplement it is used to advance sleep onset or reset circadian rhythm disruption from shift work or travel.
How it works
Melatonin binds to MT1 and MT2 receptors in the suprachiasmatic nucleus — the brain's central circadian clock. This reduces neuronal firing and promotes sleep initiation. It does not increase total sleep duration significantly in people without circadian disruption — its primary role is in timing sleep onset, not deepening sleep.
What the research says
- 0.5mg is as effective as 5mg for improving sleep onset, with fewer next-day grogginess effects (Lewy et al., 2002)
- Effective for jet lag, shift work adjustment, and delayed sleep phase syndrome
- Less effective as a standalone treatment for chronic insomnia compared to sleep hygiene and cognitive behavioural therapy
- Improves sleep quality in athletes during periods of heavy training
Effective dose
0.5–1mg taken 30–60 minutes before intended sleep time. This is significantly lower than most commercial products which contain 5–10mg per tablet. Higher doses are not more effective for sleep onset and increase the likelihood of morning grogginess and circadian disruption with regular use.
What to check on the label
Most Australian melatonin supplements are sold at 1–5mg. Look for the lowest available dose — 0.5mg if possible, otherwise 1mg tablets that can be halved. Avoid products combining melatonin with multiple other sleep ingredients as they make it impossible to assess what is actually working.
Safety
Safe for short-term use in healthy adults. Long-term effects of supplemental melatonin on endogenous production are not fully established. In Australia melatonin above 2mg is prescription-only (Circadin). Not recommended for children without medical supervision.