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Diagnostic process - history, examination and investigation

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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Unlike diabetic ketoacidosis (DKA) which presents within hours of onset, HHS comes on over many days (1).

  • typical patient is an elderly person with undiagnosed diabetes or type 2 diabetes managed by diet and/or oral diabetic medication
  • history will reveal one or more of the precipitating factors (often medication) (1,2)

HHS patients may present with:

  • weakness
  • visual disturbance
  • leg cramps
  • nausea and vomiting - less frequent than in patients with DKA
  • neurological symptoms - degree of neurologic impairment correlates directly to the effective serum osmolarity
    • lethargy, confusion
    • hemiparesis (often misdiagnosed as cerebrovascular accident)
    • seizures - present in up to 25% of cases, can be generalized, focal, myoclonic jerking, or movement induced
    • coma (2)

Physical finding will reveal

  • signs of severe dehydration e.g. - poor tissue turgor, dry buccal mucosa membranes; soft, sunken eyeballs; cool extremities; and a rapid, thready pulse
  • low grade fever
  • abdominal distension - due to gastroparesis induced by hypertonicity (2)


  • blood glucose - markedly raised (usually 30 mmol/L or more)
  • serum osmolarity - elevated >320 mmol/L (normal range is 290 ± 5 mmol/L)
    • serum osmolarity is useful, both as an indicator of severity and for monitoring the rate of change with treatment
    • if measurement of total osmolality is not available, osmolarity should be calculated as a surrogate using the formula 2(Na) + glucose + urea.
  • arterial blood gases
  • urinalysis
  • renal function tests and electrolytes
  • creatinine, blood urea nitrogen (BUN)


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