Episodes of excessive sweating that occur during sleep. Night sweats can be severe and soak a person’s bedclothes and bed sheets, which may cause the person to wake up. Night sweats are a common symptom of menopause. They may also be caused by illness or medical conditions, such as infection, cancer, low blood sugar, hormone disorders, and neurologic conditions. They may also be a side effect of certain medicines, cancer treatment, too much caffeine or alcohol, or tobacco or drug use.