What is the optimal timing for taking melatonin (a hormone regulator) for a person traveling from New York to London to alleviate jet lag?

Melatonin Timing for New York to London Travel

For travel from New York to London (5-hour eastward time zone shift), take melatonin 5 mg at 10 PM local time in London (starting the first night after arrival), NOT in New York before departure. Your proposed timing of 6 PM in London would be too early and could cause daytime sleepiness while delaying adaptation to local time. 1, 2

Optimal Timing Strategy

After Arrival in London

• Take 5 mg of immediate-release melatonin between 10 PM and midnight London time (close to target bedtime at destination) for 3-4 days after arrival 1, 2
• This timing aligns with the melatonin phase response curve, where evening dosing (after the DLMO - dim light melatonin onset) produces phase advances needed for eastward travel 3
• Taking melatonin at 6 PM London time is too early and risks causing premature sleepiness and interfering with circadian adaptation 1, 2

Before Departure from New York

• Do NOT take melatonin at 10 PM in New York (which would be 3 AM London time) - this timing would be counterproductive 1, 2
• If you want to pre-adapt before travel, you would need to advance your sleep schedule by 1 hour per day for 3-5 days before departure, taking melatonin at progressively earlier times 4
• However, this pre-flight strategy is complex and most travelers should simply wait until arrival 4

Dosing Recommendations

• Use 5 mg immediate-release melatonin rather than lower or higher doses 1, 2
• The 5 mg dose helps people fall asleep faster and sleep better compared to 0.5 mg, while doses above 5 mg show no additional benefit 1, 2
• Avoid slow-release formulations as they are less effective for jet lag 1, 2

Duration of Treatment

• Continue for 3-4 nights after arrival in London 1, 2
• The number needed to treat (NNT) is 2, meaning melatonin is highly effective for eastward travel across 5 time zones 1, 2

Critical Timing Pitfall

• Taking melatonin at the wrong time (early in the day at your destination) will cause sleepiness and delay adaptation to local time - this is the most important caveat 1, 2
• Your proposed 6 PM timing in London falls into this problematic early window 1, 2

Safety Considerations

• Melatonin is safe for occasional short-term use in healthy adults 1, 2
• Use caution if you have epilepsy or take warfarin, as case reports suggest potential harm 1, 2, 5
• Choose reputable formulations (USP Verified when possible) as melatonin is a dietary supplement with variable quality control 5, 6

Why Eastward Travel Is Harder

• Eastward travel (New York to London) causes more severe jet lag than westward travel because humans naturally have circadian periods slightly longer than 24 hours, making phase delays easier than phase advances 1, 2, 7
• The benefit of melatonin is greater for eastward flights and when crossing more time zones 1, 2