Electrolytes & Fluids

Insulin + dextrose (K-shifting)

Emergency potassium shifting for life-threatening hyperkalemia in dogs and cats. Regular insulin drives K from extracellular fluid into cells; concurrent dextrose prevents iatrogenic hypoglycemia. Onset 15–30 min, K reduction 0.5–1.2 mEq/L lasting 4–6 hr. Typically paired with calcium gluconate and definitive treatment of the underlying cause.

Regular insulin U-100 + 50% dextrose

Regular insulin only. Humulin R or Novolin R. NPH, lente, glargine, detemir, and degludec are NOT appropriate for this protocol; wrong pharmacokinetics. Use a U-100 insulin syringe for accuracy. Read the vial.
Dilute D50 before IV bolus. Undiluted D50 (~2500 mOsm/L) causes phlebitis. Standard: dilute with equal volume of 0.9% NaCl to D25 for the bolus, or further into 50–100 mL saline (final D5–D10) given over 5–10 minutes.
Insulin shifts K; it does not remove K. Total-body K is unchanged. Effect lasts only 4–6 hr. The K problem fundamentally resolves only when the underlying cause is addressed (deobstruction in UTO, mineralocorticoid replacement in Addisonian crisis, dialysis or diuresis in AKI). Do not delay definitive treatment.
Rebound hypoglycemia for 4–6 hours. Monitor BG every 1 hour × 6 hours. Run 2.5–5% dextrose CRI in maintenance fluids during this window. Symptomatic hypoglycemia in cats can be subtle (weakness, lethargy, decreased mentation).

Hyperkalemia emergency workflow

Insulin/dextrose is one of three drug-therapy components of life-threatening hyperkalemia management, alongside calcium gluconate (membrane stabilization) and fluid therapy. See the hyperkalemia emergency hub for the full workflow including ECG-finding criteria, step ordering, deobstruction or mineralocorticoid replacement as applicable, and monitoring.

Species

Dog Cat

Patient weight

lb kg

Insulin dose (U/kg)

Range 0.25–0.5 U/kg. Default 0.25 (lower end). Higher doses do not reliably lower K further but increase hypoglycemia risk.

Dextrose ratio (g per U insulin)

Range 1–2 g per unit of insulin. Default 2 (the safer ratio for hypoglycemia prevention). Lower ratios (closer to 1) may be acceptable in diabetic patients with established hyperglycemia, but are NOT routine for blocked cats or Addisonian patients.

Awaiting input

Enter a patient weight to see the result.

Reference

How the calculation works

Insulin dose × weight gives total units. Dextrose is paired at a fixed ratio of g per unit of insulin. D50 stock is 0.5 g/mL:

$$\text{total insulin (U)} = \text{dose}_{\text{U/kg}} \times \text{weight}_{\text{kg}}$$

$$\text{dextrose (g)} = \text{total insulin (U)} \times \text{ratio}_{\text{g/U}}$$

$$\text{D50 volume (mL)} = \frac{\text{dextrose (g)}}{0.5_{\text{g/mL}}}$$

Worked example with current inputs

Enter a patient weight to see the worked example.

Sources

Cooper ES. Urethral Obstruction. In: Silverstein DC, Hopper K, eds. Small Animal Critical Care Medicine. 3rd ed. Elsevier; 2023. Chapter 122 (cites regular insulin 0.25–0.5 U/kg IV with concurrent dextrose 1–2 g per unit insulin).
DiBartola SP. Disorders of Potassium. In: Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice. 4th ed. Elsevier; 2012. Chapter 5 (overview of hyperkalemia mechanisms and therapy).