Trips, shifts and late nights

Can you take melatonin during the day?

By GyroscopeUpdated November 15, 20267 sources

Mostly no. Melatonin makes people drowsy whatever the hour, and taken in the morning it can move your body clock later, which is the opposite of what most people want. The two exceptions are a small dose late in the afternoon to move your bedtime earlier, and a dose before day sleep after a night shift.

It’s easy to think of melatonin as a night pill that does nothing in daylight. Your own melatonin only shows up after dark, so it seems like a tablet at noon should just sit there until evening. But a tablet reaches your blood within the hour whatever the time, and your body takes the message the same way.

A daytime dose makes you sleepy

In 1994, researchers gave 20 men doses from 0.1 to 10 mg at 11:45am. Every dose made them sleepier, lowered their body temperature and lowered their scores on a test of staying alert. Even the smallest doses, which only raised their blood to a normal night’s level, did it.

Age makes it last longer. The US National Center for Complementary and Integrative Health says melatonin may stay active longer in older people and cause daytime drowsiness. Don't drive after a dose.

The morning is the wrong hour

The hour you take melatonin decides which way it moves your body clock. In a 2010 lab study, a dose in the afternoon moved people’s clocks earlier, and a dose just after waking moved them later. It’s like setting your watch back every morning and wondering why you can’t get to sleep at night.

The jet lag research found the same thing. Taken early in the day, melatonin “is liable to cause sleepiness and delay adaptation”, which is why every trip plan here puts the dose at bedtime in the new time zone.

When a daytime dose makes sense

To move your bedtime earlier. This is the one daytime dose that’s on purpose. Taken 2 to 4 hours before your own melatonin starts, a small dose pulls your clock earlier. If you wake at 7am on days with no alarm, your melatonin probably starts around 8:45pm, so the window is 0.5 mg between 4:45 and 6:45pm. A dose that small is back under your own night’s peak by about 7:05 to 7:30pm, so it’s mostly gone before bed. The melatonin window below works out yours.

After a night shift, before day sleep. In trials melatonin added about 24 minutes of daytime sleep after night shifts, on low-quality evidence, and didn’t help people fall asleep faster. If you try it, take it once you’re home and before your sleep block, never before you drive. The night shift planner builds the rest of the day around it.

What about naps?

For an ordinary afternoon nap there’s no good reason to take it. A daytime dose can leave you sleepy and less alert for the rest of the afternoon, and taken late in the day it starts moving your clock, which changes your nights too. A dark, quiet room does the job without either.