Mild sweating at night is often environmental — a hot room, heavy bedding, nightwear, alcohol, spicy food, or a passing fever. Hormonal changes such as menopause or perimenopause are a very common cause in women. Anxiety and some medicines, including certain antidepressants, can also trigger night sweats.
Regular, soaking night sweats that drench your bedclothes deserve a doctor's review. Possible causes include infections (such as tuberculosis in some settings), thyroid overactivity, low blood sugar in people on diabetes treatment, and, less commonly, certain cancers such as lymphoma.
See a doctor sooner if night sweats come with unexplained weight loss, persistent fever, swollen glands, a lasting cough, or extreme fatigue. A clinician can take a history and arrange tests if needed. This is general information, not a diagnosis.