Night sweats are a relatively common symptom, with many possible causes. Virtually anything that causes excessive daytime sweating will cause night sweats. The most common include fever, usually caused by infections. Some medications can cause night sweats. Night sweats are often caused by the hormonal changes sparked by menopause and perimenopause in women over 40. Other common causes of night sweats include obesity, pregnancy, excess alcohol intake, caffeine and spicy food. Another possible cause is ‘hypoglycaemia’ (low blood sugar), for example from diabetes medication, including tablets and insulin. Sometimes, night sweats can be a sign of an over-active thyroid gland, particularly if associated with weight loss, loose stools and palpitations. Other times no obvious cause is detected, despite severe persistent night sweats. This is known as idiopathic hyperhidrosis
In Chinese medicine, night sweats denote deficient yin and a relative excess of heat in the body.