Excessive night sweats have a wide range of causes, from hormonal shifts and medications to sleep disorders and, less commonly, serious infections or cancers. Up to 41% of primary care patients report night sweats, making it one of the most common symptoms people experience but rarely mention to their doctors. In fact, only about 12% of patients who have night sweats actually bring it up at a medical visit. Understanding the most likely causes can help you figure out whether your sweating is a nuisance or a signal worth investigating.
Hormonal Changes and Menopause
The single most common cause of night sweats in women between their late 30s and mid-50s is the drop in estrogen that comes with perimenopause and menopause. Lower estrogen levels make the body’s internal thermostat, located in a brain region called the hypothalamus, overly sensitive to tiny changes in body temperature. When the hypothalamus misreads a slight rise in temperature as overheating, it launches a cooling response: blood vessels near the skin dilate, heart rate increases, and sweat glands activate. During sleep, this shows up as a drenching night sweat that can soak through clothing and sheets.
These episodes peak in frequency and intensity during the menopausal transition and can persist for years. Men also experience hormonal night sweats, though less commonly, when testosterone levels drop significantly due to aging, medical treatment, or conditions affecting the testes.
Medications, Especially Antidepressants
Several widely prescribed medications cause night sweats as a side effect, and antidepressants are the most frequent culprits. SSRIs cause excessive sweating in roughly 7% to 19% of patients, depending on the specific drug. Clinical trial data puts the range at 3% to 11%. The sweating can occur during the day, at night, or both, and it sometimes begins weeks after starting the medication.
Other medication categories linked to night sweats include blood pressure drugs, hormone therapies, diabetes medications that can cause low blood sugar overnight, and over-the-counter fever reducers like aspirin or acetaminophen. If your night sweats started shortly after beginning a new medication, that timing is worth noting for your doctor. In many cases, adjusting the dose or switching to a different drug resolves the problem.
Obstructive Sleep Apnea
Sleep apnea is an underrecognized cause of night sweats. A large Icelandic study found that about 31% of men and 33% of women with obstructive sleep apnea reported frequent night sweats (three or more times per week), compared with just 9% of men and 12% of women in the general population. That makes night sweats roughly three times more common in people with untreated sleep apnea.
The mechanism ties back to the repeated airway collapses that define the condition. Each time your airway closes during sleep, oxygen levels drop and your nervous system fires up to reopen it. This stress response raises blood pressure and activates sweat glands. The encouraging finding from the same study: once patients used a continuous positive airway pressure (CPAP) machine successfully, their sweating rates dropped back to general population levels. If you snore heavily, wake up gasping, or feel exhausted despite a full night’s sleep, sleep apnea may be driving your sweats.
Infections
Night sweats are a hallmark symptom of several infections, ranging from common viruses to serious bacterial diseases.
- Tuberculosis is one of the classic causes. In its reactivated pulmonary form, TB typically presents with a persistent cough, low-grade fever, weight loss, and night sweats several times per week.
- Infectious mononucleosis (caused by the Epstein-Barr virus) can trigger night sweats during the acute phase, particularly if you’ve recently had an upper respiratory infection.
- HIV/AIDS frequently causes fever with or without night sweats, either from the virus itself or from related complications like opportunistic infections.
- Endocarditis, an infection of the heart valves, produces night sweats along with fever, chills, and fatigue. The sweating is thought to result from bacteria periodically entering the bloodstream and causing spikes in body temperature overnight.
- Fungal infections like histoplasmosis and coccidioidomycosis can mimic tuberculosis, producing cough, weight loss, and night sweats, especially in people living in regions where these fungi are endemic.
Infection-related night sweats almost always come with other symptoms: fever, unintentional weight loss, fatigue, or a persistent cough. Isolated night sweats without any other signs are unlikely to point to a serious infection.
Cancer, Particularly Lymphoma
Night sweats are one of the “B symptoms” used to stage lymphoma, a cancer of the immune system’s lymph nodes. The sweats associated with lymphoma are typically described as drenching, soaking through pajamas and bedding. They’re usually accompanied by unexplained weight loss, persistent fatigue, and fevers or chills. Swollen lymph nodes in the neck, armpits, or groin are another common sign.
It’s important to keep this in perspective. Lymphoma is a relatively rare cause of night sweats compared to hormonal changes, medications, or sleep apnea. But the pattern matters: drenching sweats that persist for weeks, combined with weight loss you can’t explain or lumps you can feel, warrant prompt evaluation. Other cancers, including leukemia and certain solid tumors, can also cause night sweats, though less characteristically than lymphoma.
Alcohol, Caffeine, and Other Lifestyle Factors
Sometimes the cause is simpler than a medical condition. Alcohol dilates blood vessels and disrupts normal sleep cycles, raising your body temperature and making overnight sweating more likely. Caffeine stimulates the nervous system, increasing heart rate and metabolism in ways that make it harder for your body to regulate temperature during sleep. Spicy foods can have a similar effect. Avoiding all three in the two to three hours before bed often reduces or eliminates sweating in people whose night sweats are lifestyle-driven.
Your sleep environment also plays a role. Heavy bedding, memory foam mattresses that trap heat, and warm room temperatures can all push your body past its comfort zone overnight. These factors don’t cause true pathological night sweats, but they can amplify sweating that’s triggered by something else.
When Night Sweats Are a Red Flag
Night sweats on their own are common and, in most cases, not dangerous. The prevalence peaks between ages 41 and 55, largely driven by hormonal changes. Among people older than 65, only about 5% develop new-onset night sweats in any given year.
The sweats that deserve closer attention are the ones that come with company. Unintentional weight loss, persistent fevers, new lumps or swollen lymph nodes, a cough that won’t resolve, or severe fatigue alongside drenching sweats suggest something beyond a warm bedroom or a glass of wine before bed. Sweats that are new, persistent over several weeks, and severe enough to soak your sheets consistently are also worth bringing up with a doctor, even if no other symptoms are present.