Diabetic ketoacidosis in the cat: phosphorus and potassium
10-year-old cat with diabetic ketoacidosis treated for 24 h with fluids supplemented with potassium chloride and a constant-rate infusion of regular insulin. It is now weaker and the microhaematocrit plasma is pink.
| Parameter | Result | Reference |
|---|---|---|
| Phosphorus | 0.9 mg/dL | 3.0–6.5 |
| Potassium | 2.7 mEq/L | 3.5–5.2 |
| Haematocrit | 22% (36% on admission) | 30–45 |
| Glucose | 240 mg/dL | 70–150 |
What is the most likely cause of the anaemia and what should you do?
chevron_right Show answer and explanation
A. Haemolysis due to hypophosphataemia: supplement IV potassium phosphate
Correct. Insulin and correction of acidosis shift phosphorus and potassium into cells. With phosphorus < 1 mg/dL, red cells lose ATP and lyse. Replace part of the potassium chloride with potassium phosphate and monitor phosphorus, potassium and magnesium every few hours.
B. Immune-mediated haemolytic anaemia: start prednisolone
Primary IMHA is uncommon in cats, and here the haemolysis coincides with severe hypophosphataemia after starting insulin. Corticosteroids would worsen glycaemic control.
C. Haemodilution from fluid therapy: reduce the fluid rate
Fluid therapy lowers the haematocrit somewhat, but not this much and not with pink plasma. Haemolysed plasma indicates red cell destruction.
D. Increase potassium chloride and keep insulin unchanged
It corrects only potassium and ignores phosphorus, which is the cause of the haemolysis and also contributes to the muscle weakness.
lightbulb Key takeaway
In ketoacidosis, total body phosphorus and potassium are depleted even if the initial value is normal: insulin shifts them into cells. Measure potassium before starting insulin and monitor phosphorus, potassium and glucose every 4–8 h during treatment.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.