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

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.

Trials comparing 0.3mg to 5mg or 10mg consistently show 0.3mg produces equal or better sleep effects with no morning grogginess Zhdanova 2001. The 3-10mg products that dominate the retail shelf are 10-30x the optimal dose.

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.

“Doses in the 0.3-0.5mg range produce sleep effects equal or superior to the 3-10mg doses commonly marketed, with no next-day grogginess. Higher doses produce supraphysiological levels that persist into the next morning and downregulate receptors over time.”

— Zhdanova et al., Clin Pharmacol Ther, 2001 view source

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