Hyperosmolar hyperglycaemic state in the dog: how to correct it
11-year-old neutered male Bichon Frise, with no previous diagnosis, polyuria and polydipsia for weeks, and anorexia and vomiting for 3 days. He presents stuporous and 10% dehydrated.
| Parameter | Result | Reference |
|---|---|---|
| Glucose | 850 mg/dL | 70–120 |
| Sodium | 156 mEq/L | 142–152 |
| Potassium | 4.1 mEq/L | 3.8–5.4 |
| Urea | 110 mg/dL | 20–50 |
| Calculated osmolality | 385 mOsm/kg | 290–310 |
| pH / bicarbonate | 7.31 / 17 mmol/L | 7.35–7.45 / 18–24 |
| Blood ketones | Negative | Negative |
What is the most appropriate initial approach?
chevron_right Show answer and explanation
A. Regular insulin infusion from admission to lower glucose quickly
Lowering glucose (and osmolality) abruptly shifts water into neurons that have generated idiogenic osmoles, risking cerebral oedema. Insulin before rehydration also moves water and glucose into cells and may worsen hypovolaemia.
B. Isotonic crystalloid first; insulin later and at a lower dose
Correct. The priority is to restore volume with an isotonic crystalloid; fluid therapy alone lowers glucose considerably. Insulin is introduced a few hours later and at a lower dose than in ketoacidosis, aiming for a slow fall in effective osmolality to avoid cerebral oedema.
C. Hypotonic fluid (0.45% NaCl) from the outset for the hypernatraemia
In a hypovolaemic patient, hypotonic fluid expands volume poorly and lowers osmolality too fast. Measured sodium will also rise as glucose falls (water moves back into cells): this is expected and does not justify hypotonic fluids at the outset.
D. Intravenous bicarbonate for the acidosis, then subcutaneous insulin
The acidosis is mild (mainly lactic, from hypoperfusion) and corrects with fluids; bicarbonate is not indicated. Subcutaneous insulin is absorbed erratically in a dehydrated patient.
lightbulb Key takeaway
In the hyperosmolar hyperglycaemic state the major risk is cerebral oedema from rapid correction. Rehydrate with an isotonic crystalloid, introduce insulin later and at a lower dose than in ketoacidosis, and make sure corrected sodium and osmolality fall gradually.
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Updated: November 1, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.