How alcohol affects your sleep
Two or three drinks can cut into REM sleep, and heavier drinking breaks up the second half of the night. What the research shows, dose by dose.
Key takeaways
A 2025 analysis of 27 studies found alcohol disrupts REM sleep from a low dose, roughly two US standard drinks for an average-sized adult, and the effect grows with each extra drink.
Alcohol only shortened the time it took to fall asleep at high doses, around four or more US standard drinks for an average-sized adult.
Early in the night alcohol can deepen sleep, but as the body clears it, the second half of the night turns lighter and more broken.
In a study of 4,098 adults, heart rate in the first hours of sleep rose by 1.4 to 8.7 beats per minute depending on how much they drank.
A few small studies found tolerance to alcohol’s sedating effect within three nights of regular drinking, which may push people to drink more for the same effect.
What alcohol does to a night of sleep
Alcohol changes sleep in two phases. While it’s still in the blood, it acts as a sedative and can push the first part of the night toward deeper sleep. Once it’s been broken down, sleep in the second half of the night becomes lighter and more fragmented, with more waking. A review of alcohol and the sleeping brain describes alcohol as initially acting as a sedative, with sleep disrupted in the second half of the night.
REM sleep takes the clearest hit. REM is the stage most linked to vivid dreams, and it normally gets longer toward morning (see what are the stages of sleep? for how the night is put together). Alcohol delays the first REM period and shortens REM overall.
The first half of the night
At high doses, alcohol does help people nod off sooner. The evidence for smaller amounts isn’t as strong. A 2025 meta-analysis of 27 studies in healthy adults found no significant change in the time it took to fall asleep across all doses combined. A shorter wait appeared only at a high dose of about 0.85 grams of alcohol per kilogram of body weight.
Early deep sleep follows a similar pattern. The time it took to reach deep sleep shortened only at an even higher dose, about 0.95 grams per kilogram. In the two studies that looked at the first three hours of sleep separately, deep sleep rose with the dose, by about 6 to 10 minutes.
The second half of the night
The picture changes as the body clears the alcohol. Breath alcohol falls by about 0.01 to 0.02 percentage points an hour, according to a review published in the National Institute on Alcohol Abuse and Alcoholism’s research journal. From a peak of 0.06% to 0.08%, the review estimates, it would be gone within about four to five hours of falling asleep, which leaves several hours of the night to run without it.
That’s when sleep tends to turn. Researchers describe more wake time and more light stage 1 sleep in the second half, especially at higher doses, and the review treats this as a rebound once the alcohol is fully metabolized. Alcohol also increases urine output, which may add to night-time waking.
Why REM takes the biggest hit
REM doesn’t hold up well against alcohol. In the 2025 meta-analysis, the first REM period arrived 18 minutes later on average after drinking, and total REM fell by about 11 minutes. Both effects grew with the dose. Each extra gram of alcohol per kilogram of body weight delayed the first REM period by about 30 minutes and cut REM by about 40 minutes.
Those REM effects showed up at a low dose, at or below 0.5 grams per kilogram, which works out to about two and a half US standard drinks for a 154-pound adult.
Across all the studies, total sleep time and time awake during the night didn’t change significantly. The one study that analyzed women separately used a high dose, about 1.1 grams per kilogram, and there drinking cut total sleep by about 19 minutes and added about 15 minutes of waking.
How much alcohol it takes
Most of the research measures alcohol in grams per kilogram of body weight. In the US, one standard drink holds about 14 grams of pure alcohol, the amount in a 12-ounce beer at 5%, a 5-ounce glass of wine at 12%, or a 1.5-ounce shot of 40% spirits, according to the National Institute on Alcohol Abuse and Alcoholism. The table converts the research doses for an adult who weighs 154 pounds (70 kilograms).
Dose | US standard drinks for a 154-pound adult | What the 2025 meta-analysis found |
|---|---|---|
0.35 g/kg | About 1.75 | Delay to the first REM period became significant |
0.50 g/kg | About 2.5 | Less REM sleep overall |
0.85 g/kg | About 4.25 | Faster sleep onset, along with greater REM disruption |
The same number of drinks won’t land the same way for everyone. Lighter people reach each dose with fewer drinks, and heavier people need more. Women also tend to reach higher blood alcohol levels than men after drinking the same amount.
Changes in heart rate and breathing
Alcohol changes how the heart behaves during sleep. A study of 4,098 adults compared each person’s nights with and without alcohol over the first three hours of sleep. Heart rate rose by 1.4 beats per minute after low intake, 4.0 after moderate intake, and 8.7 after high intake. Heart rate variability, which reflects the calming side of the nervous system, fell in step. Being young or physically active didn’t protect against these effects. The study relied on people’s own reports of how much they drank.
Breathing isn’t spared either. A 2018 meta-analysis found that higher alcohol consumption was linked to a 25% higher risk of sleep apnea, possibly because alcohol makes the upper airway more likely to collapse. The authors recommend advising people with or at risk of sleep apnea against drinking.
Drinking to sleep
It’s not clear the sedating effect lasts with regular use. The NIAAA-journal review reports that tolerance to alcohol’s sedative and sleep-stage effects developed within three nights. A later review counts only five such studies, with 24 people in total, and notes that their results are inconsistent.
That’s a trap for people who drink to sleep. The NIAAA-journal review reports that about 30% of people with persistent insomnia had used alcohol to help them sleep in the previous year. The review of alcohol and the sleeping brain describes a cycle in which alcohol is used to fall asleep, the poor sleep that follows brings daytime sleepiness, and that leads to more drinking.
Frequently asked questions
Does one glass of wine affect sleep?
A small amount has a smaller effect, but it isn’t zero. In the study of 4,098 adults, low intake raised heart rate during the first hours of sleep by about 1.4 beats per minute. The meta-analysis found REM effects starting at around 0.35 grams per kilogram, which is close to two standard drinks for a 154-pound adult.
Does alcohol help you fall asleep?
At high doses it can, but the pooled research found no clear effect at lower doses. Even when alcohol shortens the time to fall asleep, the meta-analysis notes that it likely makes the later REM disruption worse.
Why do I wake up at 3am after drinking?
At the peak levels used in lab studies, the NIAAA-journal review estimates alcohol would be cleared within about four to five hours of falling asleep, which for someone asleep at 11pm means around 3am to 4am. Sleep after that point tends to become lighter and more broken as a rebound, and higher urine output may add to the waking.
How long before bed should you stop drinking?
The research doesn’t set a cutoff. It does estimate that, from the levels used in lab studies, alcohol takes about four to five hours to clear after falling asleep, and the disruption follows the clearing. The more alcohol there is to clear, the longer it lasts into the night.
ABOUT THIS ARTICLE
This article explains research on sleep in general and isn’t medical advice. If you have symptoms that worry you, or sleep trouble that lasts more than a few weeks, talk to a doctor.