Melatonin safety and recommended dosage
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Melatonin Safety: Short-Term and Long-Term Use
Melatonin is widely used for sleep disorders and other health conditions, and its safety profile is generally favorable. Short-term use of melatonin at low to moderate doses (up to 5–6 mg daily) is considered safe, with minimal and reversible side effects such as sleepiness. Most studies have not found significant differences in adverse effects between melatonin and placebo, even with long-term use in certain populations, such as children with sleep disorders and adults with autism spectrum disorder 310. Laboratory tests, including liver function, remain normal even with higher doses, and no significant interactions with other medications have been observed .
In children, melatonin has been shown to be safe and effective for delayed sleep–wake phase disorder, with no serious adverse effects reported in both short-term and long-term studies. Long-term use (up to 10 years) did not negatively impact sleep quality, puberty development, or mental health . Animal studies also support the absence of genotoxic or carcinogenic effects, even at very high doses .
However, there is limited data on the long-term safety of melatonin in adults, especially beyond six months of daily use. Potential concerns include effects on reproductive function and puberty timing, particularly if used during pregnancy or lactation, but these have not been substantiated in healthy adults using standard doses .
Recommended Dosage of Melatonin: Adults and Older Adults
General Adult Population
For most adults, the optimal dose of melatonin for sleep improvement is not firmly established, but doses between 1 mg and 6 mg are commonly used and appear effective for improving sleep, with some studies suggesting that 4 mg/day may maximize benefits for sleep onset and duration 67. Higher doses, up to 10 mg, have also been used without significant safety concerns, but increasing the dose above this range does not necessarily improve sleep outcomes .
Older Adults
In older adults, melatonin levels naturally decline, and supplementation can help with circadian rhythm disorders. Studies recommend using the lowest possible dose of immediate-release melatonin to mimic natural circadian rhythms and avoid prolonged, high blood levels. Doses as low as 0.5 mg to 6 mg have been studied, with no clear dose-response relationship for sleep improvement, so starting with the lowest effective dose is advised 47.
High-Dose Melatonin
Some clinical and research settings have used much higher doses of melatonin (40–200 mg/day) for specific conditions, such as severe sleep disorders or as an adjunct in severe viral infections like COVID-19. Even at these high doses, studies have not found evidence of toxicity or adverse effects on liver function, and long-term use (over four years) has been reported as safe in older adults 12. For severe viral infections, doses up to 8 mg/kg/day have been suggested, divided into multiple sub-doses, and are considered safe based on clinical and animal data .
Melatonin Dosage in Children
For children, especially those with delayed sleep–wake phase disorder, melatonin is effective and safe when used at the minimal effective dose, typically 3–6 mg, and administered at the correct time before bedtime. Long-term studies have not shown negative effects on development or health, but it is recommended to periodically stop treatment to reassess the need .
Special Considerations and Formulation Variability
Melatonin supplements are not regulated in some countries, such as the United States, leading to variability in product content and quality. This lack of regulation means that the actual melatonin content may differ from what is stated on the label, so caution is advised when selecting products .
Conclusion
Melatonin is generally safe for short-term and long-term use at low to moderate doses (up to 6 mg daily) in adults and children, with minimal side effects. Higher doses have also been used safely in specific clinical situations. The lowest effective dose should be used, especially in older adults and children, to mimic natural melatonin rhythms and avoid unnecessary exposure. While current evidence supports the safety of melatonin, especially for sleep disorders, more research is needed on its long-term effects in the general population and in special groups such as pregnant or lactating women.
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