Night sweats happen when you sweat during sleep even though your bedroom isn’t unusually hot. They’re surprisingly common, and the causes range from a room that’s a few degrees too warm to hormonal shifts, medications, and occasionally something that needs medical attention. Most of the time, the explanation is straightforward and fixable.
Normal Sweating vs. Night Sweats
Your body temperature naturally dips during sleep as part of your circadian rhythm. To cool itself down, your body sometimes sweats, and that’s completely normal. The difference between routine overnight perspiration and true night sweats comes down to one question: is your environment causing it, or is something internal going on?
If you’re sleeping under a heavy comforter, wearing thick pajamas, or your room is above 70°F, your body is doing exactly what it should. That’s a normal cooling response. Night sweats in the medical sense mean sweating that happens even when your sleep environment is cool and comfortable. People with true night sweats often wake up with damp or soaked sheets regardless of what they’re wearing or how cool the room is.
Your Bedroom Might Be Too Warm
Before looking for a medical explanation, check the simplest one first. Sleep experts at the Cleveland Clinic recommend keeping your bedroom between 60 and 67°F (15 to 19°C). Anything above 70°F is considered too hot for quality sleep, and humidity makes it worse because sweat can’t evaporate efficiently. A room that feels fine when you climb into bed can become noticeably warmer overnight, especially if you share it with a partner, a pet, or both.
Memory foam mattresses and synthetic bedding also trap heat. Switching to breathable materials like cotton sheets, wearing light or moisture-wicking sleepwear, and using a fan can make a significant difference. If the sweating stops after these changes, you likely never had a medical issue at all.
Hormonal Changes Are the Most Common Medical Cause
For women in perimenopause or menopause, night sweats are extremely common. About 75% of perimenopausal and postmenopausal women in Western countries experience hot flashes, and many of those flashes happen during sleep. The underlying mechanism involves more than just declining estrogen levels. When estrogen drops, it affects brain chemicals involved in temperature regulation, particularly norepinephrine. This narrows what’s called your thermoneutral zone, the range of core body temperatures your brain considers “normal.” With a narrower zone, even a tiny increase in body temperature can trigger a full sweating response that would normally require a much bigger temperature change.
These episodes can start years before periods actually stop and continue for years after. They tend to be most intense in the first one to two years after menopause begins. Men aren’t immune either. Low testosterone, which becomes more common with age, can cause similar temperature regulation problems and nighttime sweating.
Medications That Cause Night Sweats
Several common medications list sweating as a side effect, and many people don’t make the connection. The most frequent culprits include:
- Antidepressants, particularly SSRIs and SNRIs, which affect the same brain chemicals involved in temperature control
- Hormone therapy, including drugs used for breast cancer or prostate cancer treatment
- Diabetes medications that lower blood sugar, since a blood sugar drop during sleep triggers a stress response that includes sweating
- Methadone and some other opioid-related medications
If your night sweats started around the same time you began a new medication, or if you recently changed your dose, that’s worth discussing with whoever prescribed it. Sometimes adjusting the timing or dose resolves the problem. Don’t stop a medication on your own to test this theory.
Sleep Apnea and Nighttime Sweating
Obstructive sleep apnea, the condition where your airway repeatedly closes during sleep, is an underappreciated cause of night sweats. Research shows that about 19% of people with sleep apnea experience night sweats compared to roughly 12% of people without it. The connection appears to be related to drops in oxygen levels. When your body struggles to breathe, it mounts a stress response that includes elevated heart rate, blood pressure spikes, and sweating.
If your night sweats come with loud snoring, gasping awake, morning headaches, or daytime exhaustion, sleep apnea is worth investigating. Treating the apnea, usually with a device that keeps the airway open during sleep, often resolves the sweating along with the other symptoms.
Infections and Immune Responses
Your body raises its temperature to fight infections, and sweating is how it brings that temperature back down. This is why night sweats are common with the flu, COVID-19, or any illness that causes a fever. The sweating typically peaks as a fever breaks, which often happens overnight.
Certain chronic infections are known for producing persistent night sweats even without an obvious fever during the day. Tuberculosis is the classic example, though it’s uncommon in many countries. HIV, endocarditis (an infection of the heart valves), and some fungal infections can also cause ongoing nighttime sweating. These would typically come with other symptoms like prolonged fatigue, weight loss, or recurring fevers.
When Night Sweats Signal Something Serious
In rare cases, persistent night sweats can be an early sign of lymphoma or another blood cancer. The sweating associated with lymphoma has a distinctive quality: it’s often described as “drenching,” meaning it soaks through your clothes and bedding to the point where you need to change the sheets. This isn’t the kind of sweating where you wake up feeling damp. It’s dramatically more intense.
Doctors look for a specific cluster of symptoms sometimes called “B symptoms”: drenching night sweats, unexplained weight loss of more than 10% of your body weight over six months, and recurring fevers. Swollen lymph nodes in the neck, armpits, or groin, persistent fatigue, and chills can also be part of the picture. Any one of these symptoms on its own usually has a benign explanation, but the combination warrants prompt evaluation.
Other Medical Causes Worth Knowing
An overactive thyroid gland speeds up your metabolism and can make you feel hot and sweaty around the clock, including during sleep. Anxiety disorders and PTSD can also trigger night sweats, since your nervous system remains in a heightened state even while you sleep. Acid reflux, particularly when it disrupts sleep, sometimes triggers sweating episodes. And in people with diabetes, low blood sugar episodes during the night produce a distinctive pattern of sweating along with restlessness, nightmares, or waking up with a headache.
What Your Doctor Will Want to Know
If you’ve ruled out environmental factors and the sweating persists for more than a few weeks, it’s reasonable to bring it up at a medical appointment. Your doctor will likely ask how long it’s been happening, how severe it is, whether you’ve had any fevers or weight changes, and what medications you take. Basic blood work can help rule out thyroid problems, blood sugar issues, signs of infection, and blood cell abnormalities that might point toward something more serious.
Keep in mind that for many people, no specific cause is ever found. Night sweats can be idiopathic, meaning they happen without a clear medical reason. That’s frustrating, but it also means nothing dangerous is being missed. In those cases, managing the environment (cool room, breathable bedding, lighter sleepwear) is the most effective strategy, and for most people, it’s enough to make the problem manageable.