What happens when you stop drinking for a month?
Measurable things change in a month. In a 2018 study of 94 moderate to heavy drinkers who chose a dry month, insulin resistance fell 26%, blood pressure about 6% and weight 1.5%. The group that kept drinking didn’t change.
A dry month gets treated as a detox fad, or sold as a way to drop a lot of weight fast. The real changes are quieter and more useful than either. They show up in blood tests and blood pressure, and the first one shows up on your watch within days.
What we’d do
Try a dry week first, and watch your overnight heart rate on your own watch or ring against a usual week. If you like what you see, go for the month. If you drink heavily every day, talk to a doctor before you stop, because withdrawal can become dangerous.
What the study did
Researchers at University College London followed healthy people who drank more than 64 g a week (men) or 48 g (women). 94 of them chose to stop for a month, and 47 chose to keep drinking. The dry group had been drinking about 258 g a week before, about 18 US drinks.
A dry month is an experiment you run on yourself, and this one came with a comparison group, so the changes weren’t just the time of year.
| After one dry month | Change |
|---|---|
| Insulin resistance (HOMA score) | down 25.9% |
| Systolic blood pressure | down 6.6% |
| Diastolic blood pressure | down 6.3% |
| Weight | down 1.5% |
| VEGF, a cancer-related growth factor | down 41.8% |
| EGF, another one | down 73.9% |
None of these changes were explained by changes in diet, exercise or smoking, and the group that kept drinking saw no change. People picked their own group, so it wasn’t a randomized trial, and it was one center in London.
Systolic (top number) and diastolic (bottom number) are the two numbers in a blood pressure measurement. bloodpressure.guide covers how drinking moves them in does alcohol raise blood pressure.
What your watch sees first
Your night heart rate moves fastest. In a 2025 study, 40 adults wore a smartwatch for nine days. Three evenings of drinking raised their average night heart rate from 63.6 to 66.6 bpm, and it fell back to 64.9 in the three dry days after.
In 20,968 WHOOP members, each drink above a person’s usual came with a higher sleeping heart rate and lower HRV that night, so a dry week takes away the cost of every drinking night in it. WHOOP paid for that study.
Test it on yourself
- Wear the same device every night for a usual week.
- Take a dry week, with the same bedtime as much as you can.
- Compare the two weeks’ average overnight heart rate, and HRV if your device shows it.
If the dry week sits clearly lower on heart rate, you’ve seen what your drinks cost your nights. The Your week tool shows how much of each usual night your drinks reach.
Who shouldn’t just stop
If you drink heavily every day, withdrawal can start within 8 hours of your last drink and can become life-threatening, according to MedlinePlus. Talk to a doctor first, and see is it dangerous to stop drinking suddenly.
4 sources
- Mehta G and others, Short-term abstinence from alcohol and changes in cardiovascular risk factors, liver function tests and cancer-related growth factors, BMJ Open, 2018pubmed.ncbi.nlm.nih.gov
- Strüven A and others, The Impact of Alcohol on Sleep Physiology: A Prospective Observational Study on Nocturnal Resting Heart Rate Using Smartwatch Technology, Nutrients, 2025pmc.ncbi.nlm.nih.gov
- Grosicki GJ and others, Real-world effects of alcohol on heart rate, sleep, and physical activity by age and sex, PLOS Digital Health, 2026 (funded by WHOOP)pubmed.ncbi.nlm.nih.gov
- MedlinePlus, Alcohol withdrawal, reviewed January 1, 2025medlineplus.gov
