Melatonin is one of the most effective over-the-counter tools for reducing jet lag, but the timing of when you take it matters far more than the dose. In clinical trials, travelers who timed melatonin correctly scored 37 points better on a 100-point jet lag severity scale compared to those taking a placebo. The key is understanding that melatonin doesn’t just make you sleepy. It actually resets your internal clock, and when you take it determines which direction that clock shifts.
Why Timing Matters More Than Dose
Your brain has a master clock that controls when you feel awake and when you feel tired. Melatonin works on this clock in two ways: it has an immediate sedative effect, and it physically shifts the clock’s timing forward or backward depending on when you take it. This is why swallowing a pill at the wrong hour can actually make your jet lag worse. Taken in the evening, melatonin pushes your clock earlier (a “phase advance”), which helps you adjust to eastward travel. Taken in the morning, it pushes your clock later (a “phase delay”), which helps with westward travel.
Your body’s lowest core temperature, which occurs roughly 4 to 5 hours before your normal wake-up time, is the pivot point. Melatonin taken before that low point advances your clock. Melatonin taken after it delays your clock. You don’t need to measure your temperature. Just think in terms of your habitual bedtime and wake time, and the guidelines below will keep you on the right side of that pivot.
Eastward Travel: The Harder Direction
Flying east (say, New York to London or Los Angeles to Tokyo) forces you to fall asleep earlier and wake up earlier than your body wants. Your internal clock naturally drifts later, not earlier, so eastward adjustment is slow, averaging about 1 hour per day. A flight crossing six time zones east could leave you struggling for nearly a week without intervention.
To speed things up, take melatonin in the early evening at your destination. For maximum clock-advancing effect, research suggests taking a low dose (0.5 mg) about 5.5 hours before your usual bedtime, or a standard dose (3 mg) about 6.5 hours before your usual bedtime. In practical terms, if you normally fall asleep at 11 p.m. back home, you’d take it around 4:30 to 5:30 p.m. home-body time. Once you arrive, the simplest approach is to take it at your destination’s local bedtime each night. This anchors your sleep to the new schedule while pulling your internal clock forward.
If your trip crosses more than eight time zones east, be cautious. Your body may try to adjust by delaying (going the long way around) rather than advancing, which can cause several days of confusion. In these cases, sticking to local bedtime dosing is the safest strategy.
Westward Travel: Usually Easier
Westward travel requires you to stay up later and sleep later, which aligns with your body’s natural tendency to drift. Most people adapt at about 1.5 hours per day heading west, compared to 1 hour per day heading east. Many travelers crossing just two or three time zones westward won’t need melatonin at all.
If you do need help (typically for flights crossing five or more zones west), the strategy flips. You want to delay your clock, so take melatonin in the morning at your destination. The CDC notes that taking melatonin when your internal clock thinks it’s morning produces the phase delay needed for westward adjustment. In practice, this means taking a small dose shortly after waking for the first few days at your destination. Avoid taking it at bedtime after westward travel, as that could advance your clock in the wrong direction.
Choosing the Right Dose
Clinical trials have tested doses ranging from 0.5 mg to 10 mg. The consistent finding is that 0.5 mg and 5 mg produce similar clock-shifting effects. The main difference is that 5 mg helps people fall asleep faster and report better sleep quality. A 3 mg immediate-release tablet is the standard dose recommended by the NHS for jet lag, and it hits a practical sweet spot between clock-shifting and sleep-promoting effects.
One important detail: immediate-release formulations work better than slow-release ones. In a head-to-head comparison, a 5 mg immediate-release tablet outperformed a 2 mg slow-release formulation for jet lag symptoms. Slow-release melatonin delivers the hormone over several hours, which blurs the precise timing signal your clock needs. Look for standard or “quick release” tablets rather than extended-release versions.
How Many Days to Take It
The typical protocol is to take melatonin for up to 5 days after arrival at your destination. Some travelers also start 1 to 3 days before departure to begin shifting their clock in advance, though the evidence for pre-departure dosing is less robust than for post-arrival use. If you’re crossing only a few time zones, 2 to 3 nights after arrival may be sufficient. For long-haul flights crossing 8 or more zones, using it for the full 5 days gives your clock the best chance to fully reset.
Stop taking it once you feel adjusted. Continuing melatonin beyond 5 days for jet lag purposes isn’t recommended and hasn’t been studied for that use.
A Quick-Reference Protocol
- Eastward, fewer than 8 zones: Take 0.5 to 5 mg at local bedtime each night for up to 5 days after arrival.
- Eastward, 8 or more zones: Same as above, but expect a longer adjustment period. Stick with local bedtime dosing.
- Westward, 5 or more zones: Take 0.5 to 3 mg in the morning at your destination for 2 to 4 days. Avoid evening dosing.
- Westward, fewer than 5 zones: You likely don’t need melatonin. Your body will adjust naturally within a couple of days.
Who Should Be Careful
Melatonin is generally well-tolerated for short-term use, but it interacts with several common medications. It can worsen blood pressure control in people taking blood pressure drugs, and it may affect blood sugar levels in people on diabetes medications. If you take anti-seizure medications, melatonin could reduce their effectiveness. It also has an additive sedative effect when combined with central nervous system depressants (including alcohol) and hormonal contraceptives.
People with autoimmune conditions should avoid melatonin, as it can stimulate immune activity. And because melatonin is metabolized by specific liver enzymes, it can interact with other drugs processed by the same pathways. If you take prescription medications daily, check with a pharmacist before adding melatonin to your travel kit.
Pairing Melatonin With Light Exposure
Melatonin works best as part of a broader strategy. Light is the strongest signal for resetting your internal clock, and combining timed light exposure with melatonin produces faster adjustment than either alone. After eastward travel, seek bright morning light at your destination and avoid bright light in the evening. After westward travel, do the opposite: get plenty of evening light and wear sunglasses in the early morning if you wake before local dawn.
Other practical steps that help include staying hydrated during the flight, avoiding heavy meals at odd hours, and resisting the urge to nap for more than 20 minutes during the day at your destination. Melatonin handles the clock-shifting biology, but these habits prevent you from accidentally undoing its effects with poorly timed sleep or light exposure.