What is the recommended dose of melatonin (melatonin) for adults?

Recommended Melatonin Dosing for Adults

For adults with delayed sleep-wake phase disorder (DSWPD), use 5 mg of melatonin administered between 19:00-21:00 (7-9 PM) for at least 28 days, while melatonin should NOT be used for chronic insomnia as it provides no clinically meaningful benefit. 1

Clinical Decision Algorithm

Step 1: Identify the Sleep Disorder Type

If the patient has chronic insomnia (difficulty falling or staying asleep without circadian misalignment):

• Do NOT prescribe melatonin 1, 2
• The American Academy of Sleep Medicine explicitly recommends against melatonin for chronic insomnia based on trials showing only a 9-minute reduction in sleep latency with 2 mg doses—a clinically insignificant improvement 1, 2
• Meta-analyses demonstrated no meaningful improvements in sleep onset, total sleep time, wake after sleep onset, or sleep quality 1
• Consider FDA-approved hypnotics or cognitive-behavioral therapy for insomnia (CBT-I) instead 1, 2

If the patient has delayed sleep-wake phase disorder (DSWPD) or circadian rhythm misalignment:

• Proceed with melatonin 5 mg 1
• This represents the evidence-based dose that showed reduction in sleep latency by 38-44 minutes and increased total sleep time by 41-56 minutes 1

If the patient is blind with non-24-hour sleep-wake rhythm disorder (N24SWD):

• Use melatonin 0.5-10 mg (doses between 0.5-10 mg show similar efficacy for entrainment) 3
• The odds ratio for entrainment with melatonin versus placebo is 21.18, meaning melatonin is ~21 times more likely to achieve circadian entrainment 3
• Administer either 1 hour before preferred bedtime or at a fixed time (21:00) 3

Step 2: Timing is Critical

For DSWPD patients:

• Administer melatonin 1.5-2 hours before the desired sleep onset time, NOT at bedtime 1
• The typical window is 19:00-21:00 (7-9 PM) 1
• Common pitfall: Taking melatonin too early in the day can cause daytime sleepiness and paradoxically delay adaptation to the desired sleep schedule 4

For blind patients with N24SWD:

• Administer 1 hour before preferred bedtime or at 21:00 fixed time 3

Step 3: Duration of Treatment

• Continue melatonin for a minimum of 28 days to properly assess efficacy 1
• For blind patients with N24SWD, treatment duration in trials ranged from 26-81 days 3
• For chronic insomnia in elderly (if used despite recommendations against it), trials used 3-12 weeks 5

Age-Specific Considerations

For elderly adults (≥55 years):

• The American Academy of Sleep Medicine specifically advises against melatonin for chronic insomnia in older adults based on very low quality evidence from 2 mg dose trials 1
• If melatonin is used for circadian disorders in elderly patients, use the lowest possible dose of immediate-release formulation (0.5-2 mg) to mimic physiological circadian rhythm and avoid prolonged supra-physiological levels 6
• Slow-release 2 mg formulation taken 1-2 hours before bedtime may improve sleep quality in primary insomnia over 3-12 weeks, though this contradicts AASM guidelines 5
• Important caveat: Melatonin secretion decreases with age, and elderly insomniacs with documented low endogenous melatonin levels may respond better to supplementation 5, 7

Formulation Matters

• Immediate-release melatonin shows superior efficacy compared to slow-release formulations 3
• The relative ineffectiveness of 2 mg slow-release melatonin suggests that a short-lived higher peak concentration works better for circadian phase shifting 3
• For elderly patients with primary insomnia specifically, slow-release 2 mg formulation may be preferred to mimic physiological secretion 5

Safety Profile and Contraindications

• Melatonin is generally well-tolerated with minimal adverse effects at recommended doses 2, 5, 8
• No serious side effects have been described in clinical trials, and there are no withdrawal symptoms 3, 5
• Critical warnings: Case reports suggest potential harm in patients with epilepsy and possible interaction with warfarin—these patients require careful monitoring or avoidance 4
• Side effects are mild even at high doses, with no evidence of dependence 8

Special Populations

Patients with comorbid depression:

• The 5 mg dose recommendation for DSWPD applies equally to adults with or without comorbid depression 1

Patients with neurological diseases:

• In mild cognitive impairment (MCI) and Alzheimer's disease with sleep disorders, use 2-5 or 10 mg as add-on treatment 5
• Prescribe as early as possible in the disease course for long-term use 5
• Light therapy administered 12 hours before melatonin has positive synergistic effects 5
• In REM sleep behavior disorder, immediate-release melatonin should be prescribed first-line due to better side effect profile than clonazepam 5

Jet lag prevention:

• Melatonin 0.5-5 mg taken close to target bedtime (10 PM-midnight) at destination is remarkably effective for flights crossing ≥5 time zones 4
• The number needed to treat is 2, with greater benefit for eastward flights 4
• Doses above 5 mg appear no more effective than 5 mg 4