Insulin IM intermittent (DKA)
Intermittent IM regular insulin for diabetic ketoacidosis in dogs and cats. An alternative to the IV CRI protocol when continuous infusion isn't practical: limited pump availability, patient can't stay on a line, or staffing constraints. Workflow has two modes: a single loading dose, then hourly doses titrated against the BG drop measured each hour.
- Regular crystalline insulin only. Do NOT use lispro, aspart, NPH, glargine, detemir, or any long- or ultra-short-acting form for this protocol.
- IM route only. Do not give SC in a dehydrated DKA patient, absorption is unreliable. Switch to SC long-acting insulin only after rehydration and once the patient is reliably eating and drinking.
- Goal: BG decline ≤ 50–75 mg/dL/hr toward < 250 mg/dL. Re-check BG hourly. If BG fails to drop into the 50–75 mg/dL target band over multiple cycles, reassess hydration, electrolytes, and concurrent disease; consider switching to IV CRI for finer titration.
Loading: first dose at admission, fixed at 0.2 U/kg IM. Then re-check BG in 1 hour and switch to Subsequent mode, entering the previous and current BG to get the next IM dose.
Enter a patient weight to see the result.
How the calculation works
Each IM dose is weight-based. Total units and draw volume from U-100 stock:
In subsequent mode, the BG drop over the previous hour determines the next dose from the Hoehne sliding scale. The target band is 50–75 mg/dL/hr:
Worked example with current inputs
Enter a patient weight to see the worked example.
Enter a patient weight to see the worked example.
Enter previous and current BG to see the worked example.
Hoehne IM sliding scale
Reproduced from Hoehne SN, in Silverstein & Hopper 3rd ed. Ch. 73 (citing Macintire 1993). Initial dose 0.2 U/kg IM, then hourly IM injections dosed by the BG drop in the previous hour.
| Previous-hour BG drop | Next IM dose | Interpretation |
|---|---|---|
| BG drop > 75 mg/dL/hr | 0.05 U/kg IM | Glucose is dropping too fast. Reduce dose to 0.05 U/kg to slow the rate. Confirm fluid composition is appropriate (consider adding 2.5% dextrose if BG approaching 250 mg/dL). |
| BG drop 50–75 mg/dL/hr | 0.1 U/kg IM | Glucose is dropping at the target rate. Continue at 0.1 U/kg. This is the desired band. |
| BG drop < 50 mg/dL/hr | 0.2 U/kg IM | Glucose is not dropping fast enough. Increase dose to 0.2 U/kg. If multiple sequential cycles fail to drop BG into the target range, reassess hydration, electrolytes, and concurrent disease, consider switching to IV CRI for finer titration. |
Currently-matched tier is highlighted (in subsequent mode). The 50–75 mg/dL/hr drop band is the desired target; both faster and slower decline trigger a dose change in the next cycle.
Electrolytes and monitoring
Same electrolyte cautions apply as for the CRI protocol: hypokalemia, hypophosphatemia, and hypomagnesemia commonly worsen as DKA therapy progresses. Monitor every 4–6 hours initially.
- Potassium: KCl CRI per /hypokalemia sliding scale.
- Phosphate: KPhos CRI 0.03–0.12 mmol/kg/hr IV; subtract its K contribution from total K supplementation.
- Magnesium: MgSO₄ CRI 0.25–1 mEq/kg/day for documented hypomagnesemia.
- Bicarbonate: only if arterial pH < 7.0 after 1 hr of fluid therapy; one-third to one-half of calculated dose.
Re-check BG every hour. As BG approaches 250 mg/dL, add 2.5% dextrose to the IV fluids; step to 5% dextrose at BG < 150 mg/dL; STOP insulin (the next IM dose) at BG < 100 mg/dL and continue 5% dextrose until BG recovers.
Sources
- Hoehne SN. Diabetic Ketoacidosis. In: Silverstein DC, Hopper K, eds. Small Animal Critical Care Medicine. 3rd ed. St. Louis, MO: Elsevier; 2023. Chapter 73, pp. 432–435. Intermittent IM protocol described on p. 434 (citing Macintire DK, "Emergency therapy of diabetic crises: insulin overdose, diabetic ketoacidosis, and hyperosmolar coma," Vet Clin North Am Small Anim Pract. 1995;25(3):639–650, as ref 28).
- See also /insulin-cri-dka for the IV CRI alternative protocol.