Night sweats happen when your body’s internal thermostat overreacts during sleep, triggering a sweating response that can range from mild dampness to soaking through your sheets. The causes span from a too-warm bedroom to hormonal shifts, medication side effects, and occasionally something more serious. Most of the time, night sweats have a straightforward explanation, but persistent drenching sweats deserve a closer look.
How Your Body Regulates Temperature During Sleep
Your brain has a built-in thermostat located in the hypothalamus. This region continuously monitors your core temperature and, when it rises above a set threshold, activates your sympathetic nervous system to trigger sweating across your skin. Sweat evaporates and pulls heat away from your body, cooling you back down.
Here’s what makes nighttime different: your core body temperature naturally drops while you sleep, falling from roughly 37.5°C (99.5°F) in the afternoon to about 36.3°C (97.3°F) in the early morning hours. Your hypothalamus actively drives this decline. If anything interferes with the process, whether it’s a thick comforter, a warm room, hormones, or an infection generating heat, your body compensates by sweating more aggressively than it would during the day. You’re also lying still in an insulated environment, so sweat pools rather than evaporating quickly, which is why you notice it more at night.
Hormonal Shifts Are the Most Common Cause
If you’re a woman in your 40s or 50s, hormonal changes are the most likely explanation. About 79% of perimenopausal women and 65% of postmenopausal women experience hot flashes or night sweats. The trigger isn’t simply low estrogen. It’s the withdrawal effect: when estrogen levels drop after a period of being high, your brain releases a surge of norepinephrine that narrows the range of temperatures your body considers “normal.” A tiny increase in core temperature that your body would previously have ignored now triggers a full sweating response.
Progesterone normally helps buffer these swings during the reproductive years. As both hormones become more erratic during perimenopause, night sweats can come and go unpredictably for months or years. Men aren’t immune either. Low testosterone, which becomes more common with age, can produce similar thermoregulatory disruption and nighttime sweating.
Medications That Cause Night Sweats
Antidepressants are one of the most overlooked causes. Up to 22% of people taking antidepressants experience excessive sweating, and it happens across every major class: SSRIs, SNRIs, and tricyclics. The mechanism works two ways. Some of these medications boost serotonin activity in the hypothalamus, directly disrupting temperature regulation. Others increase norepinephrine levels, which overstimulates the sweat glands themselves.
Other common medications linked to night sweats include:
- Fever-reducing drugs like acetaminophen and aspirin, which can trigger rebound sweating as they wear off overnight
- Steroids such as prednisone
- Hormone-blocking therapies used for breast or prostate cancer
- Blood pressure medications
- Diabetes medications that lower blood sugar, since hypoglycemia itself triggers sweating
If your night sweats started around the same time as a new prescription, that’s worth mentioning to your prescriber. Switching to a different medication in the same class sometimes resolves the problem.
Sleep Apnea and Nighttime Sweating
Obstructive sleep apnea has a surprisingly strong link to night sweats. About 19% of people with sleep apnea report regular night sweats, compared to 12% of the general population. The connection appears to be driven by oxygen levels: more than half of night-sweating sleep apnea patients showed low blood oxygen during sleep, compared to 37% of those without night sweats.
The mechanism makes sense when you think about it. When your airway collapses during an apnea event, your body struggles to breathe, your heart rate spikes, and your sympathetic nervous system fires up repeatedly throughout the night. Frequent awakenings and body movements increase sympathetic tone, which directly activates sweat glands. If you snore loudly, wake up gasping, or feel exhausted despite a full night’s sleep, sleep apnea could be driving both your fatigue and your sweating.
Infections and Immune System Causes
Night sweats are one of the classic signs your immune system is fighting something. Infections raise your body’s temperature set point, producing fever. As your immune system gains the upper hand and the set point drops back down, your body sweats to shed the excess heat. This cycle often peaks at night.
Tuberculosis is the infection most historically associated with night sweats, typically occurring several times per week alongside cough, weight loss, and low-grade fever. HIV infection commonly presents with fever and night sweats, particularly as it progresses. Endocarditis, a heart valve infection, produces sweats through nocturnal fever caused by bacteria periodically entering the bloodstream. Even infectious mononucleosis causes night sweats at significantly higher rates than other viral illnesses.
Acid reflux is a less obvious culprit. Case reports and literature reviews have identified gastroesophageal reflux disease as a cause of unexplained night sweats, particularly when the sweating occurs without fever. If you notice your sweating coincides with heartburn or a sour taste in your mouth, reflux may be a contributing factor.
When Night Sweats Signal Something Serious
The vast majority of night sweats have a benign cause. But certain accompanying symptoms raise the stakes and point toward possible malignancy or serious infection. The combination of drenching night sweats, unintentional weight loss (more than 5% of your body weight over six to twelve months), and persistent fever is a recognized warning pattern, particularly for lymphoma.
Hodgkin’s lymphoma in particular can present with night sweats as the only initial symptom. Patients sometimes describe high, fluctuating fevers accompanied by soaking sweats that persist for weeks. Swollen lymph nodes that feel firm, are painless, and have been present for more than four to six weeks are another red flag, especially in the neck or armpits.
Other signs that warrant a medical evaluation alongside your night sweats:
- Easy bruising or unusual bleeding
- Persistent fatigue that doesn’t improve with rest
- Unexplained weight loss
- Swollen lymph nodes that persist beyond a recent illness
- Recurring fevers without an obvious source
If none of these apply to you and your sweats are occasional, a medical cause is far less likely.
Simple Fixes for a Better Night
Before investigating medical causes, it’s worth ruling out the obvious. Your bedroom temperature should be between 60 and 67°F (15 to 19°C). Anything above 70°F is too warm for most adults. Babies and toddlers sleep best between 65 and 70°F.
Beyond temperature, a few practical adjustments can make a real difference. Moisture-wicking sleepwear and breathable bedding (cotton or bamboo rather than synthetic fabrics) allow sweat to evaporate instead of pooling. Alcohol, even moderate amounts, raises core body temperature for hours and is a well-known night sweat trigger. Spicy food and caffeine close to bedtime can have a similar effect. If you exercise in the evening, give your body at least two to three hours to cool down before sleep.
Layering lighter blankets rather than using one heavy comforter lets you shed insulation easily during the night without fully waking up. Keeping a glass of cold water by the bed won’t prevent sweating, but it helps you cool down and rehydrate when it happens.