Is 15mg of melatonin (N-acetyl-5-methoxytryptamine) too much for an adult?

Is 15mg of Melatonin Too Much for Adults?

Yes, 15mg of melatonin is generally too much for most adults and lower doses are typically more effective with fewer side effects. 1

Recommended Dosing Guidelines

• The American Academy of Sleep Medicine suggests starting with much lower doses of melatonin (3mg) for sleep disorders, with gradual titration in 3mg increments only if needed 1
• Clinical evidence indicates that effective melatonin doses for adults typically range from 1-5mg 2
• Higher doses (10mg and above) may cause receptor desensitization or saturation, potentially disrupting normal circadian signaling mechanisms 1

Evidence Against High-Dose Melatonin

• The American Academy of Sleep Medicine does not recommend melatonin for treating insomnia at all, based on trials using 2mg doses 3
• Higher doses (10mg+) are associated with more frequent adverse effects including:
  • Morning headache and grogginess 1, 4
  • Daytime sleepiness (reported in 1.66% of patients) 4
  • Dizziness (reported in 0.74% of patients) 4
  • Gastrointestinal upset 1, 4

Paradoxical Effects of Higher Doses

• Lower doses can be more effective than higher doses due to melatonin's mechanism of action on M1 and M2 receptors 1
• Higher doses may lead to receptor desensitization, reducing effectiveness while increasing side effect risk 1
• The half-life of melatonin means higher doses can remain active into morning hours, causing "hangover" effects 1

Safety Considerations

• While melatonin is generally considered safe even at higher doses, a systematic review of high-dose melatonin (≥10mg) showed an increased risk of mild adverse events compared to placebo 5
• Long-term safety data beyond several months is limited, though available evidence suggests good tolerability 1, 6
• Individual variability factors can significantly impact melatonin metabolism:
  • Concurrent medications may interact with melatonin metabolism 1
  • Patients with certain conditions (epilepsy, liver disease) may experience enhanced sensitivity 1

Practical Recommendations

• Start with 3mg of immediate-release melatonin taken 1.5-2 hours before desired bedtime 1
• If ineffective after 1-2 weeks, consider increasing by 3mg increments, but generally staying below 10mg 1, 2
• Be aware that melatonin is regulated as a dietary supplement in the US, raising concerns about purity and reliability of stated doses 1
• Use with caution in patients taking warfarin or those with epilepsy due to potential interactions 1

Important Caveats

• Most adverse events reported with melatonin are mild to moderate and resolve spontaneously within a few days or upon discontinuation 4
• No life-threatening adverse events have been identified in clinical studies 4, 5
• Quality control issues with over-the-counter melatonin products mean actual doses may vary from labeled amounts 1