Doctors often hear their patients complain of night sweats. Night sweats refer to excess sweating during the night. However, if your bedroom is unusually hot or you are wearing too many bedclothes, you may sweat during sleep, and this is normal. True night sweats are severe hot flashes occurring at night that can drench sleepwear and sheets, which are not related to an overheated environment.
In one study of 2,267 patients, 41% reported experiencing night sweats during the previous month, so the perception of excessive sweating at night is fairly common. It is important to note that flushing (a warmth and redness of the face or trunk) may also be hard to distinguish from true night sweats.
There are many different causes of night sweats. To find the cause, a doctor must obtain a detailed medical history and order tests to decide if an underlying medical condition is responsible for the night sweats. Some of the known conditions that can cause night sweats are:
Menopause. The hot flashes that accompany menopause can occur at night and cause sweating. This is a very common cause of night sweats in women.
Idiopathic hyperhidrosis. Idiopathic hyperhidrosis is a condition in which the body chronically produces too much sweat without any identifiable medical cause.
Infections. Tuberculosis is the infection most commonly associated with night sweats. But bacterial infections, such as endocarditis (inflammation of the heart valves), osteomyelitis (inflammation within the bones), and abscesses can cause night sweats. Night sweats are also a symptom of HIV infection.
Cancers. Night sweats are an early symptom of some cancers. The most common type of cancer associated with night sweats is lymphoma. However, people who have an undiagnosed cancer frequently have other symptoms as well, such as unexplained weight loss and fevers.
Medications. Taking certain medications can lead to night sweats. Antidepressant medications are a common type of drug that can lead to night sweats. From 8% to 22% of people taking antidepressant drugs have night sweats. Other psychiatric drugs have also been associated with night sweats. Medicines taken to lower fever, such as aspirin and acetaminophen, can sometimes lead to sweating. Many other drugs can cause night sweats or flushing.
Hypoglycemia. Low blood sugar can cause sweating. People who are taking insulin or oral diabetes medications may experience hypoglycemia at night that is accompanied by sweating.
Neurologic conditions. Uncommonly, neurologic conditions including autonomic dysreflexia, posttraumatic syringomyelia, stroke, and autonomic neuropathy may cause increased sweating and may lead to night sweats.