Night sweating can arise from harmless situations or serious disease. If your bedroom is unusually hot or you are using too many bedclothes, you may begin to sweat during sleep - and this is normal. In order to distinguish night sweats that arise from medical causes from those that occur because one's surroundings are too warm, doctors generally refer to true night sweats as severe hot flashes occurring at night that can drench sleepwear and sheets, and that are not related to an overheated environment. 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. Some of the known conditions that can cause night sweats include:Cancer: Night sweats are an early symptom of some cancers. The most common type of cancer associated with night sweats is lymphoma. Leukemia also may cause night sweats. However, people who have an undiagnosed cancer frequently have other symptoms as well, such as unexplained weight loss and fevers.Hypoglycemia: Sometimes low blood sugar can cause sweating. People who are taking insulin or oral anti-diabetic medications may experience hypoglycemia at night that is accompanied by sweating.Hormone disorders: Sweating or flushing can be seen with several hormone disorders, including pheochromocytoma, carcinoid syndrome, and hyperthyroidism.Neurologic conditions: Uncommonly, neurologic conditions including autonomic dysreflexia, post-traumatic syringomyelia, stroke, and autonomic neuropathy may cause increased sweating and possibly lead to night sweats.Idiopathic hyperhidrosis: Idiopathic hyperhidrosis is a condition in which the body chronically produces too much sweat without any identifiable medical cause.Infections: Classically, tuberculosis is the infection most notoriously associated with night sweats. However, bacterial infections, such as those that cause endocarditis (inflammation of the heart valves), osteomyelitis (inflammation within the bones), and abscesses all may result in night sweats. Night sweats are also a symptom of HIV/AIDS.