Myth or fact

A nightcap helps you sleep

Short answerNot the way you think

By GyroscopeUpdated November 14, 20266 sources

Not the way you think. A drink can knock you out, but across 27 studies, falling asleep faster only showed up at about four to five drinks, while REM sleep was already cut at about two. And as the alcohol runs out in the second half of the night, your sleep turns light and broken.

Why does it feel like it works?

The first part of the night really does change. You feel drowsy, you drop off, and the first few hours are heavy and deep. A 2013 review of every study of alcohol and sleep in healthy people its authors could find saw it at every dose. People fell asleep sooner and slept more solidly in the first half of the night.

Then plenty of people sleep through the part that went wrong, or wake at 3am and blame something else. The researchers behind the 2025 review started from exactly this, noting that alcohol “is commonly consumed prior to bedtime with the belief that it facilitates sleep.”

A nightcap is a loan against the second half of your night. You get a deep start up front and pay it back after 2am.

What does the drink cost you?

The same 2013 review found more broken sleep in the second half of the night at all doses, and the first REM period came late at every dose. In a lab study of 24 young light drinkers, a strong dose before bed meant more deep sleep and less REM early on, then more time awake, less deep sleep and lower sleep efficiency later. There was no REM catch-up by morning.

The 2025 review pooled 27 studies and measured the doses. REM sleep started later and was shorter after a low dose, up to 0.5 g of alcohol per kg of body weight, and the loss grew with every step up. Falling asleep faster, and reaching deep sleep faster, only showed up at 0.85 g per kg or more.

To get the one thing a nightcap is for, most people would need about four to five drinks, and by then REM is taking the biggest hit in the studies.

How long does a nightcap stay with you?

It stays a lot longer than it takes to finish. Your liver clears a fixed amount an hour, about 15 mg per 100 mL on average, so a drink taken just before bed lands right on top of your sleep.

On our engine, with a 1.5 oz pour of 40% whiskey at 10:30pm, bed at 11 and an empty stomach, here’s when it’s mostly cleared.

A single “small” nightcap reaches into the middle of the night for most bodies, and a double reaches toward morning.

What else does it do at night?

Your heart notices. In 20,968 WHOOP members, a night with one drink more than their usual, against one less, came with a sleeping heart rate 2.4 beats higher in men and 2.8 in women. Drinking an hour earlier than usual, against an hour later, came with a slightly lower heart rate that night, which is the opposite of a nightcap.

Your breathing changes too. Across 14 trials with 422 people, alcohol added about 2 breathing pauses an hour during sleep, about 4 in people who snore and about 7 in people with sleep apnea. If you snore, a nightcap costs you more than it costs most people.

The best case for a nightcap

“I fall asleep in ten minutes after a drink and I lie awake for an hour without one.” That can be true, and the 2013 review found faster sleep onset at every dose it looked at. The 2025 review, which pooled the numbers, only found it at high doses. Either way, the REM loss and the broken second half came along with it. A faster start doesn’t make up for a worse night, and the drink does nothing for whatever kept you awake in the first place.

What to do instead

• Move the drink to dinner. In our worked evening of two glasses of wine, finishing two hours earlier gave back about two hours of alcohol-free sleep. Tonight’s clear time shows yours.
• Make the bedtime drink a 0% one. Sparkling water, herbal tea or a 0% beer keeps the ritual and drops the cost.
• Use Last call to find the latest time a drink clears by your bedtime.

The two halves of a drinking night has the full science.