What is the recommended insulin (regular human insulin) regimen for treating adult diabetic ketoacidosis, including IV infusion dosing, dextrose addition, and transition to subcutaneous insulin?

Insulin Regular Regimen for Adult Diabetic Ketoacidosis

Initial Intravenous Insulin Protocol

Begin continuous IV regular insulin infusion at 0.1 units/kg/hour after confirming serum potassium ≥3.3 mEq/L, preceded by an optional IV bolus of 0.1 units/kg. 1

Insulin Solution Preparation

• Prepare 100 units of regular human insulin in 100 mL of 0.9% sodium chloride (concentration: 1 unit/mL) 1
• Prime the infusion tubing with 20 mL of the prepared solution before connecting to the patient to prevent insulin adsorption 1

Target Glucose Decline

• Aim for a glucose reduction of 50–75 mg/dL per hour during the initial treatment phase 1, 2
• If glucose does not fall by at least 50 mg/dL in the first hour despite adequate hydration, double the insulin infusion rate every hour until steady decline is achieved 1, 2

Critical Safety Check: Potassium Threshold

• Absolute contraindication: Do NOT initiate insulin if serum potassium <3.3 mEq/L—this can precipitate fatal cardiac arrhythmias 1, 2
• Hold insulin and aggressively replace potassium at 20–40 mEq/hour until K⁺ ≥3.3 mEq/L 1

Concurrent Fluid and Electrolyte Management

Initial Fluid Resuscitation

• Start with isotonic saline (0.9% NaCl) at 15–20 mL/kg/hour for the first hour (approximately 1–1.5 L in average adult) 1, 2

Potassium Replacement During Insulin Infusion

• Once K⁺ is 3.3–5.5 mEq/L and urine output is adequate, add 20–30 mEq/L potassium to each liter of IV fluid 1, 2
• Use a mixture of approximately 2/3 potassium chloride (or acetate) and 1/3 potassium phosphate 1
• Target serum potassium of 4.0–5.0 mEq/L throughout treatment 1, 2
• Monitor potassium every 2–4 hours as insulin drives potassium intracellularly 1

Addition of Dextrose to IV Fluids

When plasma glucose falls to 250 mg/dL, switch IV fluids to 5% dextrose with 0.45–0.75% NaCl while continuing the same insulin infusion rate. 1, 3, 2

• This prevents hypoglycemia while allowing continued insulin therapy to clear ketones 1, 3
• Target glucose range of 150–200 mg/dL until complete DKA resolution 1, 3
• Never stop or reduce insulin when glucose normalizes—ketone clearance requires ongoing insulin even after euglycemia 1, 3

Monitoring Requirements

Laboratory Monitoring Frequency

• Check blood glucose every 1–2 hours during active insulin infusion 1
• Measure serum electrolytes (especially potassium), venous pH, bicarbonate, anion gap, BUN, creatinine, and osmolality every 2–4 hours until metabolically stable 1, 2

Preferred Ketone Monitoring

• Direct measurement of β-hydroxybutyrate in blood is the preferred method for monitoring DKA resolution 1, 3
• Avoid nitroprusside-based urine ketone tests—they miss β-hydroxybutyrate and lag behind actual ketone clearance 1, 3

DKA Resolution Criteria

DKA is resolved when ALL of the following are met simultaneously: 1, 3, 2

• 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. 1, 3, 2

Transition Protocol

• Continue IV insulin for an additional 1–2 hours after the subcutaneous basal dose to ensure adequate absorption and prevent rebound hyperglycemia 1, 3
• Calculate basal insulin dose as approximately 50% of the total 24-hour IV insulin amount given as a single daily injection 1
• Divide the remaining 50% equally among three meals as rapid-acting prandial insulin 1

Critical Pitfall to Avoid

• Stopping IV insulin without prior basal insulin overlap is the most common cause of recurrent DKA 1, 2
• Never discontinue IV insulin abruptly—this leads to rebound ketoacidosis and hyperglycemia 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 fluid replacement can be equally effective and more cost-effective than continuous IV insulin. 1, 2

• This approach requires adequate fluid replacement, frequent bedside glucose monitoring, and appropriate follow-up 1
• Continuous IV insulin remains the standard for critically ill, mentally obtunded, or hemodynamically unstable patients 1, 2

Common Pitfalls and Safety Alerts

• Never initiate insulin when K⁺ <3.3 mEq/L—replete potassium first 1, 2
• Never hold insulin when glucose falls to 250 mg/dL—add dextrose to IV fluids instead 1, 3
• Never stop IV insulin without 2–4 hour basal insulin overlap—this causes DKA recurrence 1, 2
• Inadequate potassium monitoring and replacement is a leading cause of mortality in DKA 2
• Overly rapid osmolality correction (>3 mOsm/kg/hour) increases cerebral edema risk 2