What is a suitable dose of melatonin for a generally healthy adult patient with no known medical conditions?

Melatonin Dosing for Healthy Adults

For a generally healthy adult with no specific medical conditions, melatonin at doses of ≤10 mg daily appears safe for short-term use, though the appropriate dose depends entirely on the intended purpose—and critically, melatonin should NOT be used for chronic insomnia. 1

Context-Dependent Dosing Algorithm

Step 1: Identify the Clinical Indication

Do NOT use melatonin for chronic insomnia in adults. The American Academy of Sleep Medicine explicitly advises against this based on trials showing no clinically significant benefit at 2 mg doses for sleep onset or maintenance. 2 For chronic insomnia, consider FDA-approved hypnotics or cognitive behavioral therapy for insomnia (CBT-I) instead. 1, 2

Step 2: Appropriate Uses and Dosing

For Delayed Sleep-Wake Phase Disorder (DSWPD):

• Use 5 mg of melatonin administered between 19:00-21:00 (7-9 PM), which is 1.5-2 hours before desired sleep onset—NOT at bedtime. 2
• Continue for at least 28 days to assess efficacy. 2
• This timing is critical for circadian phase advancement and showed reductions in sleep latency of 38-44 minutes. 2

For Jet Lag Prevention:

• Use 0.5-5 mg taken close to target bedtime (10 PM-midnight) at the destination. 3
• Doses of 5 mg work faster than 0.5 mg for sleep onset, though both are effective for jet lag. 3
• Doses above 5 mg appear no more effective. 3
• Timing warning: Taking melatonin early in the day causes sleepiness and delays adaptation to local time. 3

For REM Sleep Behavior Disorder:

• Start with 3 mg at bedtime, titrating up in 3 mg increments to a maximum of 15 mg if needed. 1
• Look for U.S. Pharmacopeia Verification Mark to ensure dose accuracy, as melatonin is an unregulated dietary supplement. 1

Safety Profile

Short-Term Safety (≤3 months):

• Doses ≤10 mg daily appear safe in healthy adults based on National Academy of Sciences review. 1
• A 28-day trial of 10 mg in healthy male adults showed no adverse effects on sleep, clinical labs, or subjective measures. 1
• Meta-analysis of controlled trials (>200 subjects, ≤3 months) reported few adverse events. 1

Common Adverse Effects:

• At higher doses: headaches, somnolence, hypotension, hypertension, gastrointestinal upset. 1
• At doses ≥10 mg: increased risk of drowsiness, headache, and dizziness (Rate Ratio 1.40). 4
• Lower doses cause similar effects in patients with preexisting conditions. 1

Critical Warnings:

• Exercise caution in women of reproductive age due to potential effects on reproductive function. 1
• Avoid in patients taking warfarin due to case reports of interactions. 1
• Avoid in patients with epilepsy due to potential harm from case reports. 1
• May impair glucose tolerance in healthy women. 1
• May increase depressive symptoms. 1

Product Quality Considerations

Melatonin is NOT FDA-approved and exists as an unregulated dietary supplement in the United States. 1 This creates significant concerns:

• Purity and stated doses are unreliable across formulations. 1
• Choose products with U.S. Pharmacopeial Convention Verification Mark for most reliable dosing. 1
• Bioavailability and content vary considerably between brands. 5

Formulation Considerations

• Immediate-release formulations are recommended over prolonged-release. 1, 2
• The 2 mg slow-release formulation appears relatively ineffective, suggesting short-lived higher peak concentrations work better. 3

Long-Term Safety Data

Long-term safety studies are scarce. 1 Available data includes:

• Pediatric follow-up (mean ~4 years, doses up to 10 mg) showed no serious adverse events. 1
• Studies up to 3.8 years with doses up to 15 mg in neurodevelopmental disabilities showed no adverse events. 1
• However, systematic long-term trials in healthy adults are lacking. 4

Common Pitfalls to Avoid

• Wrong timing: Taking melatonin at bedtime for DSWPD instead of 1.5-2 hours before desired sleep onset reduces efficacy. 2, 5
• Using for chronic insomnia: This is ineffective and delays appropriate treatment. 2
• Assuming all doses are equal: 5 mg works faster than 0.5 mg for sleep onset, though circadian effects may be similar. 3
• Ignoring product quality: Unverified supplements may not contain stated doses. 1