Night sweats are surprisingly common, affecting up to 41% of primary care patients, with the highest rates among adults between 41 and 55. Most causes are benign, ranging from hormonal shifts to medication side effects to a bedroom that’s simply too warm. But persistent, drenching night sweats, especially paired with other symptoms, can signal something that needs medical attention.
Hormonal Changes Are the Most Common Cause
For many people, the answer is hormones. During perimenopause and menopause, estrogen and progesterone levels swing unpredictably, and these fluctuations affect the brain’s internal thermostat. That thermostat, which normally keeps your body temperature in a tight range, becomes more sensitive to small changes. It misreads a minor temperature shift as overheating and launches a full cooling response: blood vessels dilate, sweat glands activate, and you wake up soaked.
This isn’t exclusive to women in midlife. Men experiencing a gradual decline in testosterone can have similar episodes. Pregnancy, particularly the third trimester and the postpartum period, is another common trigger. In all these cases, the underlying mechanism is the same: shifting hormone levels destabilizing the body’s temperature control.
Medications That Trigger Sweating
If your night sweats started around the same time you began a new medication, that’s worth investigating. Antidepressants are among the most common culprits. SSRIs cause excessive sweating in roughly 7% to 19% of users depending on the specific drug, and older tricyclic antidepressants carry similar risks. Other antidepressants, including venlafaxine and bupropion, have also been clearly linked to sweating.
Beyond antidepressants, several other drug classes can cause night sweats: medications that lower blood sugar (if your blood sugar drops too low overnight), steroids, and some pain relievers. If you suspect a medication is the cause, your doctor may be able to adjust the dose or switch you to an alternative.
Alcohol and Lifestyle Triggers
Drinking alcohol, even moderately, can cause night sweats. Alcohol increases your heart rate and widens blood vessels in the skin, which pulls heat to the surface and triggers perspiration. This effect is more pronounced if you drink within a few hours of bedtime. For some people, even two or three drinks in an evening are enough to cause noticeable sweating overnight.
Other lifestyle factors worth considering: spicy food close to bedtime, caffeine late in the day, exercising in the evening, and sleeping under heavy bedding or in a warm room. These are the easiest causes to test. Try eliminating one at a time for a week and see if the pattern changes.
Sleep Apnea and Night Sweats
Obstructive sleep apnea, a condition where your airway repeatedly collapses during sleep, has a strong but often overlooked connection to night sweats. In one study, 31% of people with sleep apnea reported frequent nocturnal sweating (three or more times per week), compared to just 11% of the general population. The repeated drops in oxygen and surges in stress hormones that happen during apnea episodes are thought to drive the sweating.
If your night sweats come with loud snoring, gasping awake, morning headaches, or daytime fatigue, sleep apnea is worth discussing with your doctor. Treating the apnea often resolves the sweating.
Infections and Immune Responses
Night sweats can accompany infections, particularly ones that linger or progress slowly. Tuberculosis is the classic example. The CDC lists night sweats as a hallmark symptom of active TB disease, alongside a persistent cough lasting three weeks or longer, chest pain, weight loss, fever, and fatigue. TB remains relatively uncommon in the U.S., but it’s an important consideration for people who have traveled to or lived in areas where TB is more prevalent.
Other infections linked to night sweats include bacterial heart valve infections (endocarditis), HIV, and certain fungal infections. In all of these cases, the sweating tends to come alongside other clear symptoms: prolonged fevers, unintentional weight loss, or persistent fatigue that doesn’t improve with rest.
Thyroid and Adrenal Gland Problems
An overactive thyroid revs up your metabolism, producing excess heat that your body tries to shed through sweating, both day and night. You’d typically also notice a racing heart, unexplained weight loss, anxiety, and trembling hands.
A much rarer cause is a tumor of the adrenal gland called a pheochromocytoma. These tumors pump out surges of adrenaline and noradrenaline at random times, triggering episodes of heavy sweating, headaches, and a pounding heartbeat. This is uncommon, but it’s one reason doctors take persistent, unexplained night sweats seriously enough to run blood work.
When Night Sweats Could Signal Cancer
This is the possibility most people are worried about when they search this question, so it’s worth being specific about what doctors actually look for. Lymphoma, both Hodgkin and non-Hodgkin types, is the cancer most closely associated with night sweats. Oncologists look for a defined cluster called “B symptoms”: unexplained fevers above 100.4°F, drenching night sweats that require changing your bedclothes, and unexplained weight loss of more than 10% of your body weight over six months.
The key word is “drenching.” Cancer-related night sweats are typically severe enough to soak through your sheets, not just a light dampness on your pillow. And they almost always appear alongside at least one of those other symptoms. Fatigue, itching, and alcohol-induced pain can also occur with lymphoma, though they don’t formally count as B symptoms. Night sweats alone, without fever or weight loss, are rarely the first sign of cancer.
What a Medical Workup Looks Like
Only about 12% of people who experience night sweats actually mention them to their doctor, which means most cases go uninvestigated. If your night sweats happen regularly, interrupt your sleep, or come with other symptoms like fever, weight loss, pain, or a persistent cough, it’s worth bringing up.
Your doctor will likely start with a detailed history: when the sweats started, how severe they are, what medications you take, and whether you’ve noticed any other changes. From there, the initial workup is usually straightforward blood tests to check your thyroid function, blood sugar, inflammatory markers, and blood cell counts. These simple tests can rule out or flag most of the serious causes. If something looks abnormal, more targeted testing follows based on what the results suggest.
For the majority of people, the cause turns out to be something manageable: a hormonal shift, a medication side effect, or a lifestyle factor. Identifying the trigger is the hard part. Once you know the cause, the sweating is usually treatable or at least controllable.