How do I prepare an insulin infusion for a patient with diabetic ketoacidosis, including concentration, dosing rate, and monitoring?

How to Prepare and Administer an Insulin Infusion for Diabetic Ketoacidosis

For moderate to severe DKA, start with an IV bolus of 0.1 units/kg regular insulin followed immediately by a continuous infusion at 0.1 units/kg/hour, targeting a glucose decline of 50–75 mg/dL per hour. 1

Critical Pre-Insulin Safety Check

Do not start insulin if serum potassium is <3.3 mEq/L—this is an absolute contraindication that can cause fatal arrhythmias. 1

• Begin aggressive potassium repletion with 20–40 mEq/L added to IV fluids (using 2/3 KCl and 1/3 KPO₄) until K⁺ reaches ≥3.3 mEq/L 1
• Obtain an ECG to assess for cardiac effects of hypokalemia 1
• Once K⁺ ≥3.3 mEq/L, proceed with insulin initiation 1

Insulin Preparation and Initial Dosing

Use only regular (short-acting) insulin for IV infusion—never use rapid-acting analogs intravenously. 2, 1

Standard Protocol for Moderate-Severe DKA:

• IV bolus: 0.1 units/kg of regular insulin given as direct push 2, 1
• Continuous infusion: 0.1 units/kg/hour via IV pump 2, 1
• Preparation: Add 100 units regular insulin to 100 mL normal saline (concentration = 1 unit/mL) 1

Alternative Low-Dose Protocol (Pediatrics or Mild DKA):

• No bolus: Start directly with 0.05 units/kg/hour infusion 2, 3
• This approach may reduce hypokalemia risk, especially in malnourished patients 3

Important Preparation Note:

When using dilute insulin solutions (<40 units/L), significant insulin adsorption to plastic tubing occurs (60–80% loss). To prevent this, either:

• Use higher insulin concentrations (≥100 units/100 mL), OR
• Add 0.5–3.5% polygeline or albumin to the carrier solution 4
• In practice, most modern protocols use 100 units in 100 mL saline, which minimizes this issue 1

Concurrent Fluid Management

Begin isotonic saline at 15–20 mL/kg/hour for the first hour alongside insulin. 2, 1

• Total fluid replacement should approximate 1.5× the 24-hour maintenance requirement 1
• Add 20–30 mEq/L potassium to each liter once K⁺ ≥3.3 mEq/L and urine output is adequate 2, 1
• Target serum potassium maintenance between 4–5 mEq/L throughout treatment 2, 1

Adjusting the Insulin Infusion

If glucose does not fall by ≥50 mg/dL in the first hour, double the insulin infusion rate hourly until achieving steady decline of 50–75 mg/dL/hour. 1

• First verify adequate hydration status before increasing insulin 1
• In rare cases of extreme insulin resistance (shock, severe acidosis), doses up to 8–14 units/hour may be required 5, 6

Adding Dextrose While Continuing Insulin

When glucose reaches 250 mg/dL, switch IV fluid to D5W with 0.45–0.75% NaCl, but continue insulin infusion at the same rate. 2, 1, 7

• Critical concept: Ketonemia clears more slowly than hyperglycemia—never stop insulin just because glucose normalizes 1, 7
• Target glucose 150–200 mg/dL until full DKA resolution 2, 1
• Continue potassium supplementation in the dextrose solution 1

Special Case—Euglycemic DKA:

If initial glucose is <250 mg/dL but ketoacidosis is present, start D5W alongside normal saline from the beginning of insulin treatment 2, 1

Monitoring Requirements

Check the following every 2–4 hours until stable: 2, 1, 7

• Blood glucose (hourly initially)
• Serum electrolytes (especially potassium)
• Venous pH (adequate substitute for arterial; typically 0.03 units lower) 7
• Serum bicarbonate
• Anion gap
• Blood urea nitrogen, creatinine, osmolality

Direct measurement of β-hydroxybutyrate is preferred over urine ketones for monitoring treatment response, as nitroprusside methods only detect acetoacetate and acetone, not the predominant ketone β-hydroxybutyrate 7

DKA Resolution Criteria

DKA is resolved when ALL of the following are met: 1, 7

• Glucose <200 mg/dL
• Serum bicarbonate ≥18 mEq/L
• Venous pH >7.3
• Anion gap ≤12 mEq/L

Transition to Subcutaneous Insulin

Administer long-acting basal insulin (glargine or detemir) subcutaneously 2–4 hours BEFORE stopping the IV insulin infusion. 2, 1

• Most common error: Stopping IV insulin without prior basal insulin administration leads to DKA recurrence 1
• Continue IV insulin for 1–2 hours after giving subcutaneous basal insulin to ensure adequate absorption 1, 7
• Typical basal dose: Use ½ of the total 24-hour IV insulin amount as a single daily dose of long-acting insulin 1
• Prandial insulin: Divide the remaining ½ equally among three meals as rapid-acting insulin 1

Patient Must Meet These Criteria Before Transition:

• All DKA resolution parameters met (above)
• Able to tolerate oral intake
• Hemodynamically stable 1

Alternative Approach for Mild-Moderate Uncomplicated DKA

For hemodynamically stable, alert patients with mild-moderate DKA, subcutaneous rapid-acting insulin analogs (0.1–0.2 units/kg every 1–2 hours) combined with aggressive IV fluids can be as effective and more cost-effective than IV insulin. 2, 1

This approach requires:

• Patient alert and cooperative
• Hemodynamic stability
• Frequent bedside glucose monitoring
• Adequate fluid replacement 1

Common Pitfalls to Avoid

• Never hold insulin when glucose falls—add dextrose instead and continue insulin to clear ketones 1, 7
• Never start insulin with K⁺ <3.3 mEq/L—repletes potassium first 1
• Never stop IV insulin abruptly—overlap with subcutaneous basal insulin by 2–4 hours 2, 1
• Never use urine ketones alone to guide therapy—they lag behind serum ketone clearance and don't measure β-hydroxybutyrate 7
• Never underdose insulin in severe DKA—if acidosis persists despite adequate hydration, increase insulin to 4–6 units/hour or more with appropriate glucose supplementation 5