Night sweats can be a sign of hormonal changes, medication side effects, infections, sleep disorders, anxiety, or less commonly, certain cancers. The term refers specifically to repeated episodes of sweating heavy enough to soak through your sleepwear or bedding. Waking up a bit warm because your room is too hot or you piled on too many blankets doesn’t count. True night sweats happen regardless of your sleep environment and are drenching enough to disrupt your rest.
The causes range from completely benign to potentially serious, so what matters most is the pattern: how often they happen, how long they’ve been going on, and whether other symptoms show up alongside them.
Menopause and Hormonal Shifts
The single most common cause of night sweats is menopause. Up to 80% of women going through perimenopause and menopause experience hot flashes, and when these happen during sleep, they become night sweats. They’re driven by fluctuating and declining estrogen levels, which disrupt the body’s internal thermostat. The brain becomes more sensitive to small changes in core temperature and overreacts by triggering a sweating response to cool you down.
These episodes typically last 7 to 10 years on average, though some women experience them for longer. They can start well before periods stop entirely, during the perimenopausal transition, and continue years into postmenopause. If you’re a woman in your 40s or 50s and night sweats are your primary symptom with no fever, weight loss, or other changes, hormonal shifts are the most likely explanation.
Medications, Especially Antidepressants
Several common medications cause night sweats as a side effect, and antidepressants are the most frequent culprits. Clinical trials show that excessive sweating occurs in 7% to 19% of people taking SSRIs, a widely prescribed class of antidepressants that includes sertraline (Zoloft), fluoxetine (Prozac), paroxetine (Paxil), and escitalopram (Lexapro). SNRIs like venlafaxine (Effexor) and duloxetine (Cymbalta) carry similar risks.
Other drug categories linked to night sweats include hormone-blocking medications, certain blood pressure drugs, and drugs that lower blood sugar. If your night sweats started shortly after beginning a new medication or changing a dose, the timing is a strong clue. Stopping or switching medications on your own isn’t advisable, but it’s worth flagging the connection with whoever prescribed it.
Infections: From Common to Chronic
Night sweats are a well-known feature of several infections, though the severity and pattern differ. Tuberculosis is the classic example. In its active pulmonary form, TB typically causes a persistent cough alongside weight loss, low-grade fever, and night sweats that can occur several times per week. People with HIV are especially susceptible, often presenting with that same trio of cough, fever, and night sweats.
Other infections that produce night sweats include fungal infections like histoplasmosis and coccidioidomycosis, which can mimic TB symptoms. Endocarditis, an infection of the heart valves, causes fever, chills, fatigue, and sweats, and its early stages can be relatively silent. Even infectious mononucleosis (caused by the Epstein-Barr virus) can trigger night sweats during its acute phase, occurring more frequently than with other upper respiratory infections.
In modern medical practice, TB and lymphoma are infrequently the actual cause when someone presents with night sweats. But infections remain an important category to rule out, particularly if you have a fever, a cough that won’t go away, or have traveled to areas where these diseases are more common.
Sleep Apnea
Obstructive sleep apnea is an underrecognized cause of night sweats. Roughly 30% of people with OSA report them. Research has found the prevalence of night sweats is notably higher in people with sleep apnea compared to those without it (about 19% versus 12%), and the sweating appears to be linked to drops in blood oxygen that happen when breathing repeatedly stops and restarts during the night.
If your night sweats come with loud snoring, gasping awake, morning headaches, or daytime exhaustion, sleep apnea may be the underlying issue. Treating the apnea, usually with a CPAP device, often resolves the sweating.
Anxiety and Nocturnal Panic Attacks
Stress and anxiety activate the sympathetic nervous system, your body’s fight-or-flight response, which triggers sweating even during sleep. Nocturnal panic attacks are a more intense version of this: you wake suddenly in a state of panic, with a racing heart, difficulty breathing, and drenching sweat. These episodes happen without any obvious trigger and can feel terrifying, partly because waking up mid-panic makes it hard to tell what’s happening.
The sweating from anxiety tends to be episodic and linked to periods of higher stress, though for some people it becomes chronic. If you recognize a pattern of anxiety, racing thoughts before bed, or wake up with a pounding heart, your nervous system’s stress response is likely playing a role.
Thyroid and Other Endocrine Conditions
An overactive thyroid (hyperthyroidism) speeds up your metabolism, raising your body temperature and causing excessive sweating both day and night. Other signs include unexplained weight loss, a rapid or irregular heartbeat, trembling hands, and feeling jittery or anxious. A simple blood test can confirm or rule this out.
Rarer endocrine causes include pheochromocytoma, a tumor of the adrenal glands that triggers surges of adrenaline, and carcinoid tumors, a type of neuroendocrine tumor that can cause flushing and sweating episodes. These are uncommon but worth mentioning because their symptoms overlap with more benign causes, and they’re treatable once identified.
When Night Sweats Signal Something Serious
In the context of lymphoma and other cancers, night sweats are one of three “B symptoms” used to stage the disease. The full set includes drenching night sweats, unexplained fever above 38°C (100.4°F), and unexplained weight loss of more than 10% of body weight over six months. These three symptoms together carry diagnostic weight that isolated night sweats do not.
Night sweats alone, without other symptoms, are rarely a sign of cancer. But certain combinations should prompt a medical evaluation sooner rather than later:
- Unexplained weight loss alongside the sweats, even if gradual
- Persistent or recurring fevers without an obvious infection
- New lumps or swollen lymph nodes in the neck, armpit, or groin
- Sweats that persist for weeks and don’t improve with environmental changes
The general prevalence of night sweats in adults ranges from 10% to 41% depending on the population studied, which means most cases trace back to something manageable: hormones, medications, stress, or a sleep disorder. The pattern of accompanying symptoms, not the sweats themselves, is what separates a benign cause from one that needs urgent attention.