What is the recommended dose of melatonin for an adult patient with insomnia or a sleep disorder, considering factors such as age, medical history, and potential interactions with other medications?

Melatonin Dosing for Adult Sleep Disorders

Direct Recommendation

Do not use melatonin for chronic insomnia in adults—the American Academy of Sleep Medicine explicitly recommends against it due to lack of clinically meaningful benefit. 1, 2 However, for delayed sleep-wake phase disorder (DSWPD), use 5 mg administered between 19:00-21:00 (7-9 PM) for at least 28 days. 1, 2

Clinical Decision Algorithm

Step 1: Identify the Sleep Disorder Type

For Chronic Insomnia (difficulty falling or staying asleep):

• Melatonin is NOT recommended based on 2017 American Academy of Sleep Medicine guidelines. 1, 2
• The studied 2 mg dose showed only a 9-minute reduction in sleep latency compared to placebo—below the threshold for clinical significance. 2
• Evidence quality was very low due to publication bias, heterogeneity, and imprecision, with benefits approximately equal to harms. 1, 2
• Instead, use FDA-approved hypnotics or cognitive behavioral therapy for insomnia (CBT-I). 1

For Delayed Sleep-Wake Phase Disorder (DSWPD):

• Use 5 mg melatonin administered between 19:00-21:00 (7-9 PM). 1, 2
• This timing is critical: give 1.5-2 hours before desired sleep onset, NOT at bedtime. 1, 2
• Continue for minimum 28 days to assess efficacy. 1, 2
• This showed reduction in sleep latency by 38-44 minutes and increased total sleep time by 41-56 minutes. 1, 2

Step 2: Age-Specific Considerations

For Elderly Patients (≥55 years):

• If you proceed despite the recommendation against chronic insomnia treatment, start with 2 mg prolonged-release formulation taken 1-2 hours before bedtime. 3
• Maximum dose is 5 mg, though most evidence supports 2 mg as optimal in elderly patients. 3
• The 2 mg dose showed approximately 19 minutes reduction in sleep latency in elderly patients compared to placebo. 2, 3
• Prolonged-release formulations are strongly preferred over immediate-release to maintain sleep throughout the night and mimic normal physiological circadian rhythm. 2, 3

For General Adult Population:

• Effective doses range from 1-5 mg for adults. 4
• For adolescents, doses of 3-5 mg have been studied. 4

Step 3: Formulation Selection

Prolonged-release (sustained-release) is preferred:

• Maintains sleep throughout the night better than immediate-release. 2, 3
• Mimics normal physiological circadian rhythm. 2
• Avoids prolonged, supra-physiological blood levels that persist into daylight hours. 3

Step 4: Critical Timing Considerations

Common pitfall to avoid:

• Do NOT administer at bedtime—this is a frequent error that reduces efficacy. 2
• Correct timing: 1.5-2 hours before desired sleep onset for circadian rhythm disorders. 1, 2
• For elderly patients with insomnia (if used off-guideline), give 30 minutes to 2 hours before bedtime. 3

Step 5: Duration and Monitoring

• Minimum trial duration: 3-4 weeks to assess efficacy before considering any changes. 2
• For DSWPD, continue for at least 28 days. 1, 2
• Do not escalate dose beyond 5 mg—higher doses provide no definitive additional benefits. 2

Safety Profile and Drug Interactions

Drug interactions:

• No significant drug-drug interactions exist between melatonin and common medications including doxepin, propranolol, or SSRIs. 2, 3
• Monitor for additive sedation if patients are on multiple CNS-active medications. 2, 3
• Melatonin is NOT listed on the American Geriatrics Society Beers Criteria, representing a safer option than many alternatives in elderly patients. 2, 3

Renal or hepatic impairment:

• No specific dose adjustments are required due to favorable safety profile with minimal adverse effects. 2
• Side effects are mild even at usual doses, with no evidence of toxicity, severe side effects, or dependence even at high doses. 4

Special Population: Elderly with Documented Low Melatonin Levels

Melatonin may be most effective in:

• Elderly patients with documented low melatonin levels during sleep. 5
• Patients chronically using benzodiazepines. 5
• However, this does not override the guideline recommendation against use for chronic insomnia. 1, 2

Key Takeaway for Clinical Practice

The most important distinction is the diagnosis: Melatonin has a role in circadian rhythm disorders (DSWPD) at 5 mg dosed 1.5-2 hours before desired sleep time, but should not be used for chronic insomnia where evidence shows no clinically meaningful benefit. 1, 2 Timing matters more than dose for efficacy. 2