Sweating in your sleep, commonly called night sweats, happens when your body’s internal thermostat overreacts and triggers your sweat glands while you’re asleep. Sometimes the cause is as simple as a warm bedroom. Other times, it signals a hormonal shift, a medication side effect, or an underlying health condition worth investigating. About 9% of primary care patients report night sweats, so it’s a genuinely common experience.
How Your Body Controls Temperature at Night
Your brain has a built-in temperature control center in the hypothalamus. It works like a thermostat: when your body gets too warm, the hypothalamus sends signals through your sympathetic nervous system down to the sweat glands in your skin. Those glands release moisture, which cools you as it evaporates. During the day, triggers like exercise, hot weather, and stress all activate this system. At night, the same pathway is still active, but your body naturally drops its core temperature slightly to promote deeper sleep.
When something disrupts that process, whether it’s an overheated room, a fever, or a hormonal fluctuation, the hypothalamus can overcorrect. It floods your sweat glands with activation signals, and you wake up damp or soaking through your sheets. The distinction worth making: occasionally waking up a little warm is normal. True night sweats are drenching enough that you need to change your clothes or bedding.
Hormonal Changes Are the Most Common Cause
Estrogen and progesterone both play a direct role in how your body regulates temperature. When levels of either hormone rise or fall sharply, your body can lose its ability to hold a stable temperature during sleep. This is why night sweats are so closely tied to hormonal transitions.
Perimenopause and menopause are the most well-known triggers. As estrogen levels decline and fluctuate unpredictably, the hypothalamus becomes more sensitive to small changes in body heat, triggering sweating episodes that can range from mild dampness to full-on drenching. But menopause isn’t the only hormonal cause. Estrogen also dips right before your period, which is why some people notice night sweats during PMS. Pregnancy, thyroid disorders, and low testosterone in men can all produce the same effect through similar disruptions to temperature regulation.
Medications That Trigger Night Sweats
Several common medications can cause sweating during sleep, and many people don’t realize the connection. In a primary care study, three drug classes stood out as significantly linked to night sweats:
- Antidepressants (SSRIs): People taking these were about three times more likely to report night sweats compared to those not on them. SSRIs affect the brain chemical serotonin, which is involved in temperature regulation.
- Blood pressure medications (angiotensin receptor blockers): These carried a similarly elevated risk, roughly 3.4 times higher than baseline.
- Thyroid hormone supplements: People taking these were about 2.5 times more likely to experience night sweats, likely because the medication can push metabolic rate higher than intended.
If your night sweats started around the same time as a new prescription, that timing is worth noting. A dosage adjustment or switch to a different medication often resolves the problem.
Sleep Apnea and Nighttime Sweating
Obstructive sleep apnea, where your airway repeatedly closes during sleep, is an underrecognized cause of night sweats. When your airway closes, your blood oxygen drops. Your body responds by jolting you partially awake, which spikes your sympathetic nervous system (the same fight-or-flight system that controls sweating). Research published in The American Journal of Managed Care found that night sweats were significantly and independently associated with more severe oxygen drops in people with sleep apnea.
If you sweat at night and also snore, wake up gasping, feel unrested despite a full night’s sleep, or have a partner who has noticed you stop breathing, sleep apnea is a strong possibility. Treating the apnea, typically with a device that keeps your airway open, often eliminates the sweating.
Infections and More Serious Causes
Night sweats are a classic symptom of certain infections. Tuberculosis, HIV, heart valve infections (endocarditis), and fungal infections like histoplasmosis can all cause drenching sweats during sleep. The pattern with these infections tends to include other symptoms too: fever, cough, unexplained weight loss, and prolonged fatigue. Infectious mononucleosis can also trigger night sweats during its acute phase, sometimes following what seemed like a routine upper respiratory infection.
Certain cancers, particularly lymphoma, include night sweats as one of their hallmark symptoms. In lymphoma, doctors specifically look for what they call “B symptoms”: drenching night sweats, unexplained weight loss, and recurring fevers. Swollen lymph nodes that persist for more than four to six weeks alongside night sweats raise particular concern.
These causes are far less common than hormonal shifts or medications, but they’re the reason persistent, unexplained night sweats deserve attention rather than dismissal.
Red Flags Worth Taking Seriously
Not all night sweats need a medical workup. But certain accompanying symptoms change the picture. Pay attention if your night sweats come with any of the following:
- Unintentional weight loss you can’t explain through diet or activity changes
- Recurring fevers, even low-grade ones
- Swollen lymph nodes in your neck, armpits, or groin that don’t go away
- Easy bruising or unusual bleeding
- Persistent fatigue that doesn’t improve with rest
Any combination of these with night sweats raises the likelihood of an infectious or malignant cause and warrants prompt evaluation. Night sweats that happen a few times and resolve on their own are less concerning than those that persist for weeks.
Simple Fixes That Actually Help
For night sweats without an underlying medical cause, your sleep environment matters more than you might expect. The Cleveland Clinic recommends keeping your bedroom between 60 and 67°F (15 to 19°C) for adults. Many people sleep in rooms that are significantly warmer than this, especially in summer or in apartments where they can’t control the heat.
Beyond temperature, your bedding and sleepwear play a role. Breathable fabrics like cotton or moisture-wicking materials allow heat to escape rather than trapping it against your skin. Heavy comforters, memory foam mattresses (which retain heat), and synthetic pajamas can all push your body past its comfort threshold. Alcohol consumption close to bedtime also dilates blood vessels and raises skin temperature, which can trigger sweating in the first half of the night as your body metabolizes it.
If you’ve optimized your sleep environment and the sweating continues, that’s a useful data point. It suggests the cause is internal rather than environmental, and tracking when the sweats happen, how severe they are, and what other symptoms accompany them gives your doctor a clearer starting point for figuring out what’s going on.