Melatonin: What It Actually Does, Optimal Dose, and Why Most Products Have 10× Too Much

Educational journalism, not medical advice. Every claim here is checked against its cited sources by editor Tim Bunce — a health writer, not a physician. It isn’t specific to your situation: for health decisions, talk to your own clinician. How we work →

What melatonin actually does

Melatonin is a hormone produced by the pineal gland, secretion rising in the evening as ambient light drops and peaking in the middle of the night. Its primary role is signalling the timing of biological night to every cell in the body — not producing sleep directly. The sleepiness people associate with melatonin is downstream of this timing signal, not the primary effect.

This distinction explains the trial results. Melatonin produces:

• Modest reduction in sleep latency — 7-12 minutes faster onset in meta-analyses, similar to a placebo with a strong belief effect.
• Strong effects on circadian phase shifting — useful for jet lag and shift-work adjustment.
• Small effects on total sleep time — 8-15 additional minutes per night on average Ferracioli-Oda 2013.
• Strong effects on delayed sleep phase syndrome — people whose body clocks are shifted late.

Why 0.3-0.5mg outperforms 3-10mg

Endogenous melatonin peaks at blood concentrations corresponding to roughly 0.3mg oral intake. Higher doses produce supraphysiological levels — concentrations many times higher than the body ever produces naturally. Two problems follow:

• Receptor downregulation: chronically elevated melatonin causes the body to reduce receptor density. Effectiveness drops over 2-4 weeks of high-dose use.
• Persistent next-morning levels: high doses don’t clear by morning. The lingering signal produces grogginess, “hangover”, and disrupted next-night sleep onset.

A landmark trial in older adults with age-related insomnia tested 0.1mg, 0.3mg, and 3.0mg doses against placebo: the 0.3mg dose — which raises blood melatonin to the level the body produces naturally at night — restored sleep efficiency, while the 3.0mg dose left melatonin circulating into daylight hours and induced hypothermia, with no added sleep benefit over the 0.3mg dose Zhdanova 2001. The 3-10mg products that dominate the retail shelf are 10-30x higher than the optimal dose the trial identified.

Timing matters

Two scenarios:

• For sleep-onset insomnia: take 0.3-0.5mg at 30-60 minutes before desired sleep. The phase-advancing effect helps initiate sleep faster.
• For circadian phase delay (you can’t get to sleep until 3am despite trying earlier): take 0.3-0.5mg 4-5 hours before your current sleep-onset time. Gradually advance the dose timing earlier across 2-3 weeks.
• For jet lag eastward: take 0.3-0.5mg at destination bedtime for 3-5 nights.
• For jet lag westward: usually doesn’t need melatonin — westward shifts align with the natural drift of human circadian rhythms.

What melatonin doesn’t do

• It’s not a sedative. If you’re anxious or your sleep environment is suboptimal, melatonin doesn’t make those issues go away.
• It doesn’t maintain sleep. Melatonin helps onset but doesn’t prevent middle-of-night awakening — that’s a different mechanism (cortisol regulation, autonomic balance, sleep environment).
• It doesn’t replace sleep hygiene. Heavy late-evening eating, alcohol, blue-light exposure, and irregular schedules disrupt sleep more than melatonin can fix.
• It’s not an antidote to caffeine. Caffeine and melatonin work through different receptors; the caffeine effect on sleep remains regardless of melatonin dose.

When CBT-I beats melatonin

For chronic insomnia (persistent sleep problems lasting weeks/months), cognitive-behavioural therapy for insomnia produces effects roughly 2-3 times larger than melatonin in head-to-head trials. CBT-I addresses the cognitive and behavioural patterns that maintain insomnia (clock-watching, in-bed wakefulness, anticipatory anxiety about sleep). It’s the first-line evidence-based intervention for chronic insomnia — melatonin is the supplement people reach for first but produces smaller and less durable effects.

Practical takeaways

• Melatonin is a circadian timing signal, not a sedative. Effective for circadian problems (jet lag, shift work, phase delay) but produces small effects on garden-variety insomnia.
• Use 0.3-0.5mg, not 3-10mg. Higher doses produce next-day grogginess and lose effectiveness over weeks.
• Timing matters. Take 30-60 min before sleep for onset; 4-5 hours earlier for phase shifts.
• Doesn’t maintain sleep, doesn’t replace sleep hygiene, doesn’t counter caffeine.
• For chronic insomnia: CBT-I produces larger and more durable effects than melatonin.

References