At what time of day should an adult patient with insomnia take a melatonin tablet?

Optimal Timing for Melatonin Administration in Insomnia

For adults with insomnia, melatonin should be taken 1-2 hours before bedtime (approximately 18:00-21:00 or 6:00-8:00 PM), with the most evidence supporting administration around 18:00-19:00 (6:00-7:00 PM) for optimal circadian rhythm regulation. 1, 2, 3

Evidence-Based Timing Recommendations

Standard Adult Dosing Window

• The optimal administration time is 1-2 hours before the desired bedtime, which allows melatonin to mimic the natural physiological secretion pattern and properly regulate the sleep-wake cycle 3, 4, 5
• Administration at approximately 18:00 (6:00 PM) is specifically recommended as the standard of care for regulating sleep cycles and reducing bedtime resistance, particularly in elderly patients and those in institutional settings 2
• The American Academy of Sleep Medicine recommends taking 5 mg of melatonin between 19:00-21:00 (7:00-9:00 PM) for delayed sleep-wake phase disorder, which can be extrapolated to general insomnia management 1

Formulation-Specific Timing Considerations

• Prolonged-release (PR) melatonin 2 mg should be taken 1-2 hours before bedtime to mimic natural melatonin secretion patterns and avoid supra-physiological blood levels persisting into daylight hours 3, 4, 5
• Immediate-release melatonin can be taken closer to bedtime (30 minutes to 1 hour before) when the primary goal is sleep onset rather than circadian rhythm regulation 1, 5

Critical Dosing Context

Important Efficacy Caveat

• The American Academy of Sleep Medicine actually recommends AGAINST using melatonin for primary insomnia in adults (weak recommendation), as studies show only minimal benefit: mean sleep latency reduction of just 9 minutes compared to placebo, with small improvements in sleep quality 6
• The evidence quality is very low, and melatonin's clinical benefit for chronic insomnia is questionable compared to other pharmacologic options 6

When Melatonin May Be More Appropriate

• Melatonin is most effective in elderly patients (≥55 years) with documented low endogenous melatonin production, where 2 mg prolonged-release formulations show approximately 19-minute reduction in sleep latency 7, 3
• Better evidence exists for circadian rhythm disorders (delayed sleep-wake phase disorder) rather than primary insomnia 1
• Patients chronically using benzodiazepines or those with circadian rhythm disturbances may benefit more than those with primary insomnia 7

Practical Administration Algorithm

Step 1: Determine Appropriate Timing

• For general insomnia: Administer 1-2 hours before desired bedtime (18:00-20:00 for a 21:00-22:00 bedtime) 2, 3, 4
• For elderly patients: Use the same 1-2 hour window, preferably around 18:00-19:00 2, 3
• For circadian rhythm disorders: Take between 19:00-21:00 1

Step 2: Choose Formulation and Dose

• Start with 2 mg prolonged-release melatonin for elderly patients or those with sleep maintenance issues 3, 4
• Use 3-5 mg immediate-release for younger adults with primarily sleep onset difficulties 1
• Maximum dose should not exceed 5 mg in most cases, as higher doses may cause receptor desensitization 1, 7

Step 3: Duration and Monitoring

• Trial for at least 3-4 weeks before assessing efficacy 4, 5
• Monitor for morning grogginess, which suggests the dose is too high or timing is too late 1

Safety Considerations

• Melatonin has a favorable safety profile with minimal adverse effects and no serious drug interactions with most medications 7, 4
• Exercise caution in patients taking warfarin or those with epilepsy due to case reports of potential interactions 1, 7
• No withdrawal symptoms, rebound insomnia, or dependence have been documented 3, 4

Common Pitfalls to Avoid

• Avoid taking melatonin too close to bedtime (less than 30 minutes before), as this doesn't allow adequate time for circadian rhythm effects 2, 3
• Don't use melatonin as first-line therapy when more effective options exist (eszopiclone, zolpidem, or low-dose doxepin have stronger evidence for primary insomnia) 6, 8
• Avoid higher doses (>5 mg) initially, as they may cause receptor desensitization and morning hangover effects without improving efficacy 1, 7
• Don't expect dramatic results - the clinical benefit is modest at best for primary insomnia (9-minute reduction in sleep latency) 6