Night sweats and hyperhidrosis (daytime sweating)

Fasting laboratory tests

• FBC
• CRP
• Serum creatinine with eGFR
• AST
• ALT
• GGT
• Alkaline phosphatase
• Serum calcium (if unexplained profuse night sweats)if needednon-French guidelineThe NHS haematology pathway (Humber and North Yorkshire) includes serum calcium in the tests for night sweats ^[2]; the 2025 Scottish guidelines propose considering it for profuse unexplained night sweats ^[3]. The American AAFP review does not cite it in its tests ^[4].
• TSH
• Fasting plasma glucose
• HIV serology (if risk factor or never screened)if needednon-French guidelineRisk factor for HIV exposure, fever, weight loss or signs of immunosuppression (oral candidiasis, cachexia) ^[2,4].
• Serum protein electrophoresis (looking for a gammopathy)if needednon-French guidelineUnexplained sweats: the NHS haematology pathway includes immunoglobulins and protein electrophoresis in the tests, a monoclonal peak being a reason for haematology opinion ^[2].
• LDH (if unexplained profuse night sweats)if needednon-French guidelineProfuse unexplained night sweats: the 2025 Scottish guidelines on haematological cancers propose considering FBC, renal and liver function, serum calcium, LDH, protein electrophoresis and HIV serology, looking notably for lymphoma ^[3].
• IGRA (if tuberculosis exposure)if neededFever, cough, weight loss, tuberculosis contact, HIV infection or immunosuppression ^[4]. NABM reimbursement is limited (documented contact notably) ^[5].
• Acid-fast bacilli in sputum, microscopy and culture, 3 samples (if chest X-ray suggestive of tuberculosis)if needednon-French guidelineSuspected pulmonary tuberculosis: NICE has a chest X-ray done and then, if it suggests tuberculosis, three deep sputum samples collected, preferably including one early-morning sample, for microscopy and culture ^[6].
• 24-hour urinary metanephrines (if labile hypertension or episodes of headache and palpitations)if needednon-French guidelineParoxysmal attacks of headache, palpitations and sweating, especially with labile hypertension: suspected phaeochromocytoma ^[4].
• 24-hour urinary 5-HIAA (if flushing with diarrhoea, wheezing or hypotension)if needednon-French guidelineAttacks of cyanotic flushing with watery diarrhoea, wheezing, hypotension or oedema: suspected carcinoid syndrome; some foods and drugs distort the result ^[4].
• Blood cultures (if fever and murmur or signs of endocarditis)if needednon-French guidelineFever, new heart murmur, splinter haemorrhages, Osler nodes or Janeway lesions: suspected endocarditis ^[4].
• Monospot test (if recent upper respiratory tract infection)if needednon-French guidelineSore throat or recent upper respiratory tract infection: night sweats are more frequent in infectious mononucleosis than in other ENT infections ^[4].

Imaging

• Chest X-ray

• Primary focal hyperhidrosis (armpits, palms, soles, face; onset before 25; no sweating during sleep): no laboratory tests.
• Generalised, asymmetric, late-onset or nocturnal hyperhidrosis: tests of the "Sueurs nocturnes" tab, guided by the clinical findings.