Melatonin: A Circadian Tool -Not a Nightly Sedative

What it is

In the U.S., melatonin is a dietary supplement, not a regulated drug. The actual content can differ dramatically from what’s on the label, including over- or under-dosing and variable purity.

Melatonin works as the body’s dim-light or sleep signal. It is useful for shifting circadian timing (jet lag, delayed sleep phase, shift work) and offering a modest sleep-onset benefit in adults (~5–7 minutes earlier on average in RCTs), with stronger effects in older adults and circadian rhythm disorders.

Melatonin is not a strong tool for sleep maintenance. It does very little to prevent nighttime awakenings or staying sleep

How to use (precision matters)

• For phase shifting: 0.3–1 mg taken ~3 hours before target bedtime.

• For sleep-onset support: up to ~3–4 mg, 1-2 hours before bedtime.

• Favor reputable brands with NSF testing and aim for immediate-release for sleep onset.

New caution: preliminary long-term safety signal (AHA 2025)

A large EHR study of 130,828 adults with insomnia found that ≥12 months of documented melatonin use was associated (not causal) with:

• ~90% higher incident heart failure over 5 years (4.6% vs 2.7%).

• 3.5× higher heart-failure hospitalization (19.0% vs 6.6%).

• ~2× higher all-cause mortality (7.8% vs 4.3%).

Important context: This is observational and preliminary and cannot prove cause-and-effect. Misclassification is likely (OTC users underreporting in “non-melatonin” group in U.S.), residual confounding is possible (insomnia severity, comorbid depression/anxiety, unrecorded hypnotics), and international prescribing differences complicate the interpretation. Still, the signal raises reasonable caution about chronic, unsupervised melatonin use.

Clinical Considerations & Best Practices

• Treat melatonin as a targeted tool, not a nightly forever supplement.

• Prefer short, goal-directed use (2–4 weeks) for sleep initiation.

• Prioritize behavioral & environmental levers first (light, temperature, caffeine/alcohol timing, wind-down).

• If ongoing need persists, make sure to reassess for underlying drivers (OSA, RLS/PLMS, mood, circadian misalignment) rather than escalating the dose.

• Consider avoiding or minimizing if you have any cardiometabolic risks until higher-quality long-term data mature.

Bottom line

Melatonin can be useful and safe short-term when precisely timed. Given the new associative signal with long-term use, you should favor brief, indication-specific courses under guidance rather than chronic nightly use.