01 / Mechanism

What it actually does.

Melatonin is N-acetyl-5-methoxytryptamine, an indoleamine synthesized from serotonin in the pineal gland. Endogenous release is gated by darkness — production rises in the evening, peaks in the middle of the night, and falls in the early morning. It is a circadian signal first and a sleep-onset signal second.

The phase-shifting effect, mediated through MT1 and MT2 receptors in the SCN (suprachiasmatic nucleus), is what makes low-dose evening melatonin useful for delayed sleep-phase syndrome and for eastward jet lag. The hypnotic / sleep-onset effect — the reason people take a 5 mg gummy thirty minutes before bed — appears at higher doses and works partly through the same receptors and partly through a modest drop in core body temperature [Brzezinski 2005].

A key point that the OTC market obscures: the dose required to produce a circadian effect is about ten times smaller than the dose required for a hypnotic effect. Endogenous nocturnal peaks correspond roughly to oral doses of 0.3–0.5 mg. The 3 mg, 5 mg, and 10 mg products that dominate US shelves push plasma melatonin into the nanogram-per-milliliter range — orders of magnitude above what the body produces at night [Zhdanova 1996].

02 / Dosing

Two doses, two jobs.

Goal	Dose	Timing	Note
Phase shift (advance)	0.3–0.5 mg	4–6 hr before desired bedtime	Low dose, early evening
DSPS (delayed sleep phase)	0.3–0.5 mg	Several hours pre-bed	Combine with morning bright light
Jet lag (eastward)	0.5–3 mg	Local bedtime at destination	Adjust gradually pre-trip if possible
Sleep-onset (general)	1–3 mg	30–60 min pre-bed	Higher = not better; can paradoxically alert
Shift work	1–3 mg	At intended sleep onset	Combine with light hygiene

The OTC overdosing problem

A 2023 JAMA analysis of 25 melatonin gummy products found that 22 of 25 were inaccurately labeled, with actual melatonin content ranging from 74% to 347% of what was on the label [Cohen 2023]. The highest measured contained 31 mg in a product labeled 10 mg. If you are using melatonin, prefer a reputable solid-tablet product, ideally USP-verified, at the smallest effective dose.

03 / Timing matters more than dose

DSPS, jet lag, phase response.

Melatonin's phase-response curve has been mapped: taken in the late afternoon and early evening, it advances the circadian phase (you get sleepy earlier the next night). Taken in the morning, it delays the phase. This is the opposite of bright light, and the two are often used in combination for DSPS (delayed sleep phase syndrome, where the person's biological clock is set late and they cannot fall asleep until 3–4 AM) [Burgess 2010].

For DSPS, the right protocol is 0.3–0.5 mg of immediate-release melatonin around 5–6 hours before the current sleep-onset time, plus bright light on waking — not 10 mg at the current bedtime, which has almost no effect on phase. For jet lag, taking melatonin at local destination bedtime helps the SCN entrain to the new clock.

Tachyphylaxis (tolerance to the hypnotic effect over time) is widely reported anecdotally but inconsistently documented in trials. There is no evidence that endogenous melatonin production is suppressed by long-term exogenous use, but it remains a sensible position to use the smallest dose for the shortest time that gets the job done.

04 / Pediatric safety

The overdose surge.

Between 2012 and 2021, pediatric melatonin ingestions reported to US poison control rose by 530%, from a small fraction of pediatric calls to roughly 5% of them. Most exposures were in children aged five and under, most were unintentional, and most resolved without hospital admission — but the spike included serious outcomes: hospitalizations, mechanical ventilation in five cases, and two deaths over the decade [Lelak 2022].

The combination of gummy formats (easy for a child to mistake for candy), inaccurate dosing per gummy, and a household perception that melatonin is fundamentally safe drove the curve. The American Academy of Sleep Medicine and pediatric sleep specialists have asked parents not to use OTC melatonin in young children without clinician guidance, with exceptions for specific neurodevelopmental conditions where evidence is more established.

05 / Side effects

What's commonly reported.

Morning grogginess at higher doses. 5–10 mg products commonly cause next-day fog; 0.3–1 mg rarely does.
Vivid dreams. Reported across doses; usually benign.
Headache. Minor and uncommon.
Mood lowering or irritability. A minority of users; reversible on stopping.
Hormonal signals (theoretical). Animal data suggests effects on reproductive hormones at very high doses; not clinically demonstrated at typical human exposures.
Drug interactions. Mild — caution with sedatives, antihypertensives, and warfarin. CYP1A2 substrate; fluvoxamine markedly increases melatonin exposure.

06 / Bottom line

Where melatonin fits.

Melatonin is a precise tool used imprecisely. The right use cases — jet lag, DSPS, shift work, and short-term sleep-onset support — are real. The default OTC dose is roughly ten times what the body produces at night, and the actual content of US gummy products is only loosely tied to the label. The smallest effective dose, taken at the right time, from a reputable solid-tablet product, is the durable answer.

For the broader sleep architecture context, see the sleep topic hub, the magnesium and sleep evidence piece, and the sleep supplement stack overview.

07 / References

The evidence base.

Brzezinski A, et al. Effects of exogenous melatonin on sleep: a meta-analysis. Sleep Medicine Reviews, 2005;9(1):41–50. [Brzezinski 2005]
Zhdanova IV, Wurtman RJ, et al. Sleep-inducing effects of low doses of melatonin ingested in the evening. Clinical Pharmacology & Therapeutics, 1996;57(5):552–558. [Zhdanova 1996]
Burgess HJ, Revell VL, Molina TA, Eastman CI. Human phase response curves to three days of daily melatonin: 0.5 mg versus 3.0 mg. Journal of Clinical Endocrinology & Metabolism, 2010;95(7):3325–3331. [Burgess 2010]
Cohen PA, Avula B, Wang Y-H, et al. Quantity of melatonin and CBD in melatonin gummies sold in the US. JAMA, 2023;329(16):1401–1402. [Cohen 2023]
Lelak K, et al. Pediatric melatonin ingestions — United States, 2012–2021. MMWR Morbidity and Mortality Weekly Report, 2022;71(22):725–729. [Lelak 2022]
Auger RR, et al. Clinical practice guideline for the treatment of intrinsic circadian rhythm sleep-wake disorders (AASM). Journal of Clinical Sleep Medicine, 2015;11(10):1199–1236. [Auger 2015]
Erland LAE, Saxena PK. Melatonin natural health products and supplements: presence of serotonin and significant variability of melatonin content. Journal of Clinical Sleep Medicine, 2017;13(2):275–281. [Erland 2017]
Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database of Systematic Reviews, 2002. [Herxheimer 2002]

About this profile

Last reviewed against evidence: 2026-05-12. This profile is editorial reference content, not sponsored. Wellness Radar does not currently carry affiliate links for specific melatonin products. Educational reference, not a prescription — for pediatric sleep concerns or persistent insomnia in adults, consult a clinician familiar with sleep disorders.

Melatonin