Felis ISSN 2398-2950

Hyperosmolar hyperglycemic state

Synonym(s): HSS; Hyperosmolar diabetes mellitus; Hyperosmolar non-ketotic diabetes; Hyperosmolar hyperglycemic non-ketotic coma

Contributor(s): Dr Linda Fleeman


  • Hyperosmolar Hyperglycemic State is a less common complication of diabetes mellitus  Diabetes mellitus in cats than diabetic ketoacidosis Diabetic ketoacidosis.
  • Affected cats are often geriatric and typically present with severe hyperglycemia and dehydration.
  • Differentiation of Hyperosmolar Hyperglycemic State from diabetic ketoacidosis might not be clinically relevant:
    • The term Hyperosmolar Hyperglycemic State is preferred over Hyperosmolar Non-ketotic Diabetes because some degree of ketosis and acidosis may be present in this condition.
    • A mixed state of diabetic ketoacidosis and hyperosmolar hyperglycemic state is reported in about 30% of human patients presented for diabetic emergency. These data are not available for cats, but the situation might be similar.
  • Management is similar to that for diabetic ketoacidosis, but is crucial that plasma sodium and glucose concentrations are decreased slowly to minimize the risk of cerebral edema.



  • Absolute or relative insulin deficiency, combined with:
    • Renal insufficiency.
    • Respiratory compromise and/or congestive heart failure Heart: congestive heart failure.
    • Any disease that causes severe fluid loss and dehydration.
    • Impaired renal excretion of glucose secondary to hypovolemia.

Predisposing factors


  • Diabetes causes osmotic diuresis and compensatory polydipsia. Dehydration is inevitable if the cat cannot consume sufficient water to compensate for urinary loss.
  • Pre-existing renal or cardiac disease can predispose to impaired renal function.
  • Additional fluid losses, eg due to gastrointestinal disease, can then result in more severe dehydration.


  • Hypovolemia results in impaired renal function and prerenal azotemia Pre-renal azotemia. Urine output consequently decreases and so less glucose is excreted in urine. Blood glucose concentration then increases contributing to more severe hyperosmolality. Idiogenic osmoles are formed in the brain to protect the brain from fluid loss. Importantly, these idiogenic osmoles are cleared slowly once hyperosmolality is corrected, and so overly rapid lowering of plasma sodium and/or glucose can result in fluid shifting into the brain causing cerebral edema.


This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login


This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login


This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Kitabchi A E, Umpierrez G E, Murphy M B et al (2006) Hyperglycemia crises in adult patients with diabetes mellitus: a consensus statement from the American Diabetes Association.​ Diabetes Care 29 (12), 2739-2748 PubMed.
  • Koenig A, Drobatz K J, Beale A B et al (2004) Hyperglycemic, hyperosmolar syndrome in feline diabetics: 17 cases (1995-2001). J Vet Emerg Crit Care 14 (1), 30-40 VetMedResource.
  • Bruskiewiez K A, Nelson R W, Feldman E C et al (1997) Diabetic ketosis and ketoacidosis in cats: 42 cases (1980-1995). JAVMA 211 (2), 188-192 PubMed.

Other sources of information

  • Feldman E C, Nelson R W, Reusch C et al(2014) Canine and Feline Endocrinology. 4th edn. Saunders.
  • Schaer M (2010) Diabetic Ketoacidosis and Hyperglycemia Hyperosmolar Syndrome. In: Textbook of Veterinary Internal Medicine. 7th edn. Eds: Ettinger S J & Feldman E C. Saunders Elsevier. pp 496-500.