Melatonin: The Correct Dose, Timing, and What It Actually Does vs. What the Bottle Claims

Melatonin is not a sleep drug. It is a circadian timing signal — a hormone that tells your body when to initiate sleep, not a sedative that forces it.

That distinction explains why most melatonin users are both over-dosing and mistiming it.

What Melatonin Actually Does

The pineal gland produces melatonin in response to darkness — specifically, the absence of short-wavelength (blue) light hitting the retina. Production rises 1–2 hours before your habitual sleep time, peaks during the early sleep phase, and falls before waking [1].

Melatonin's primary functions:

• Circadian anchor. Sets the timing of the body's internal clock via MT1 and MT2 receptors in the suprachiasmatic nucleus (SCN)
• Core body temperature reduction. Induces peripheral vasodilation, lowering core temperature — a required condition for sleep onset
• Not sedative. Does not act on GABA or histamine pathways (unlike sleep drugs); has no direct effect on sleep depth or duration [1]

Melatonin works by shifting sleep timing — moving when sleep initiation occurs — not by making sleep happen with more force.

The Dosing Evidence

Standard commercial melatonin doses are 5–10mg per tablet. The pharmacologically effective dose for circadian phase shifting is 0.1–0.5mg — one-tenth to one-fiftieth of what's on the shelf.

> 📌 A 2002 pharmacokinetic study published in the Journal of Biological Rhythms by Lewy et al. found that 0.5mg of physiological melatonin administered at the correct circadian time produced equivalent phase-shifting effects to 20mg doses — and that supraphysiological doses (5mg+) produced prolonged elevated melatonin levels the following morning, impairing daytime alertness without additional circadian benefit. [1]

The 10mg tablet doesn't improve sleep. It keeps melatonin artificially elevated into the next morning.

The Timing Evidence

Melatonin is most effective when taken approximately 30–60 minutes before desired sleep onset. For circadian shifting — jet lag, shift work — it needs to be timed earlier: 2–4 hours before the new target sleep time.

If you're adjusting to a new time zone or schedule, dose timing should reference the new target, not your habitual bedtime.

When Melatonin Is and Isn't Useful

Useful:

• Jet lag (cross-timezone travel)
• Shift work schedule changes
• Delayed sleep phase disorder (chronotype late shift)

Not the correct intervention for:

• General insomnia — cognitive-behavioral therapy for insomnia (CBT-I) is the first-line evidence-based treatment
• Poor sleep quality — sleep architecture is affected by stress, screen light, room temperature, and alcohol, none of which melatonin addresses

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