Clinical investigations from the RACP

Investigation of the patient with night sweats

John H Gallo



Night sweats are a common presenting symptom that challenges the clinician to distinguish between benign conditions and a large differential of possible underlying causes.

Key Points

  • Night sweats are common; they can be a benign symptom or a manifestation of serious illness.
  • Diagnosis of the cause of night sweats relies on a thorough history and examination, supplemented by stepwise investigations in selected patients.
  • A serious underlying illness should be suspected when no obvious cause for night sweating is apparent from the history, the sweats are severe and cause drenching of sheets, they are persistent for more than one month, or they are associated with other systemic symptoms.
  • Systemic symptoms to look for include fever of 38oC or more, suggestive of an infection, autoimmune disease, endocrine disorder or malignancy, and weight loss of at least 10% body weight within six months, suggestive of an endocrine disorder or malignancy.
  • Most initial investigations of night sweats are used to detect nonspecific indicators of the presence of systemic disease.
  • Further testing will depend on the patient’s clinical features, duration of symptoms and results of preliminary tests.