Melatonin for sleep — dose, timing, evidence

Verdict

Melatonin earns its moderate evidence rating because — used correctly — it has solid effects on circadian timing problems. It loses points for being almost universally misused. Most users take 5–10 mg at bedtime expecting a sleeping pill, experience little effect, and conclude it doesn't work. They've tested the wrong protocol.

Where the evidence is strong

• Jet lag — particularly eastward, crossings of 5+ time zones. 0.5 mg at destination bedtime for 3–5 nights. Multiple meta-analyses confirm this use.
• Delayed sleep phase disorder — combined with morning bright light, melatonin is first-line treatment for chronically late natural sleep times.
• Children with neurodevelopmental sleep disorders — strongest paediatric evidence is in autism spectrum disorder and ADHD-related insomnia.

Where the evidence is weak

• Primary insomnia in adults without circadian misalignment.
• Sleep maintenance (waking in the night).
• Long-term nightly use as a sleep aid for general use.

Dose, in detail

The melatonin receptor saturates at very low doses (around 0.3 mg in many individuals). Studies comparing 0.3, 0.5, 1, 3, and 5 mg consistently find no additional phase-shift benefit from higher doses — and several find worse outcomes from high doses due to next-day residual sleepiness.

Practical recommendation: start at 0.3–0.5 mg. Most US OTC products start at 1 mg (or higher). UK pharmaceutical-grade Circadin is 2 mg prolonged-release — still relatively low.

Timing — the critical detail

For phase shifting (advancing sleep), take melatonin 4–5 hours before target bedtime. Burgess et al (2008) mapped the human phase response curve: the largest advancing effect occurs in this window, not at bedtime.

For mild bedtime sedation, take 30 minutes before sleep. The effect size is small — typically a 7–10 minute reduction in sleep onset latency. Don't expect a knockout.

Use the timing calculator for your specific bedtime.

Side effects and safety

Short-term use is well-tolerated. Common minor side effects: morning grogginess (more common at higher doses), vivid dreams, mild headache. Less common: low mood, increased appetite. No tolerance or dependency develops in the standard sense — though some users report subjective “needing it” psychologically.

Long-term safety data is limited but reassuring. The major regulatory concern is for use in adolescents, where there's theoretical concern about effects on puberty timing — most evidence in humans hasn't demonstrated this, but caution is reasonable.

The supplement quality problem

US melatonin gummies and tablets are not regulated as medications. A 2023 JAMA letter (Cohen et al) tested 25 commercial melatonin gummy products and found actual melatonin content ranged from 74% below label to 347% above. Several products also contained CBD that wasn't on the label.

Practical implications:

• Buy pharmaceutical-grade products where available (UK Circadin, US Natrol melatonin in tested-quality lines).
• Avoid gummies and exotic formulations — they're the most variable.
• Liquid sublingual or simple tablets are most predictable.

When not to use melatonin

• Pregnancy — limited safety data.
• Autoimmune conditions — theoretical immune-system interaction.
• If you're on blood thinners or anti-seizure medication — drug interactions exist.
• Children except under specialist guidance.