Excessive Sweating

Under normal conditions, 800mL of water is lost daily as insensible loss, mostly in sweat. Excessive sweating can at least double this figure. As a symptom, it is normally part of a package of other problems – it is unusual for the patient to present with excessive sweating in isolation.

Published: 2nd August 2022 | Updated: 15th August 2022

Differential diagnosis

Common Diagnoses

  • Menopause
  • Anxiety
  • Infections (Common, Acute)
  • Hypoglycaemia: May be Reactive (i.e. Non-Diabetic)
  • Hyperthyroidism

Occasional Diagnoses

  • Drugs: Alcohol, Tricyclic Antidepressants, Pilocarpine
  • Alcohol and Drug Withdrawal
  • Shock/Syncope
  • Intense Pain
  • Hyperhidrosis
  • Other Infections (e.g. TB, HIV, Endocarditis, Brucellosis, Lyme Disease)

Rare Diagnoses

  • Dumping Syndrome (e.g. Post Gastric Surgery)
  • Malignancy (e.g. Lymphoma)
  • Organic Nerve Lesions: Brain Tumours, Spinal Cord Injury (Sweating is Localised to Dermatome Involved)
  • Pachydermoperiostosis: Localised to Skin Folds of Forehead and Extremities
  • Hyperpituitarism/Acromegaly
  • Rare Vasoactive Tumours: Phaeochromocytoma, Carcinoid
  • Connective Tissue Disorders

Ready reckoner

Key distinguishing features of the most common diagnoses

MenopauseAnxietyInfectionLow GlucoseHyperthyroid
Short HistoryNoNoYesYesNo
Vasoconstricted SkinNoPossiblePossibleYesPossible
Raised Body TemperatureNoNoYesNoNo
Systemically UnwellNoNoYesYesYes

Possible investigations

Likely: FBC, ESR/CRP, TFT.

Possible: FSH/LH, LFT, glucose.

Small Print: Autoimmune screen, CXR, tests for uncommon infections, 24 h urinary 5-HIAA, 24 h urinary-free catecholamines and VMAs, CT/MRI scan.

  • FBC/ESR/CRP: ESR/CRP and WCC raised in infection. Raised ESR/CRP and anaemia possible in lymphoma and other malignancies.
  • TFTs: May reveal thyrotoxicosis as a cause of chronic sweating.
  • Glucose: In reactive hypoglycaemia only useful at the time of the sweating.
  • FSH/LH: Helps if diagnosis of menopause in doubt.
  • LFT: May reveal high alcohol intake.
  • CXR might reveal occult infection (especially TB) or malignancy.
  • Tests for uncommon infections (e.g. blood test for HIV or Lyme disease, echocardiography for endocarditis).
  • Autoimmune screen: May help in confirming diagnosis of connective tissue disease.
  • 24 h urinary 5-HIAA: If carcinoid syndrome suspected.
  • 24 h urinary-free catecholamines and VMAs: If phaeochromocytoma suspected.

Top Tips

  • Length of history is very helpful – short-term sweating is likely to have an apparent, acute cause; if long-term, the diagnosis is more likely to be constitutional or anxiety; in the medium term, the differential diagnosis is much wider.
  • Anxiety rarely causes night sweats.
  • Do not underestimate the potentially devastating effect of hyperhidrosis.

Red Flags

  • Lack of fever does not exclude infection. In some infections (e.g. TB, brucellosis) – and lymphoma – sweating can be out of phase with fever.
  • If the problem is persistent, a full examination is advisable, paying attention to the lymph nodes, liver and spleen. If no cause is apparent, have a low threshold for investigations or referral, particularly if the patient is unwell or losing weight.
  • Consider unusual infections in the recently returned traveller (e.g. TB, typhoid).
  • Episodic skin flushing (especially provoked by alcohol) with diarrhoea and breathlessness is likely to be caused by anxiety – but don’t forget carcinoid syndrome as a rare possibility.
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Website disclaimer

Pulse Reference is based on the best-selling book Symptom Sorter.

The experts behind Pulse Reference are Dr Keith Hopcroft who is the co-author of Symptom Sorter, a GP in Essex and Pulse’s editorial advisor and Dr Poppy Freeman, a GP in Camden and also a clinical advisor to Pulse.

This website is for clinical guidance only and cannot give definitive diagnostic information. Practitioners should work within the limits of their individual professional practice, seek guidance when necessary and refer appropriately.