For an adult with resolved diabetic ketoacidosis (pH > 7.3, bicarbonate ≥ 18 mmol/L, anion gap ≤ 12, potassium ≥ 3.3 mEq/L), how should I overlap subcutaneous basal insulin with the intravenous regular‑insulin infusion—what timing and dose are recommended?

Overlapping Subcutaneous Basal Insulin with IV Insulin in Resolved DKA

Administer subcutaneous basal insulin (glargine or detemir) 2–4 hours before discontinuing the IV regular‑insulin infusion to prevent rebound hyperglycemia and recurrent ketoacidosis. 1

Timing of the Overlap

The American Diabetes Association establishes a mandatory 2–4 hour overlap period between administering the first dose of long‑acting basal insulin subcutaneously and stopping the IV insulin drip. 1, 2 This window allows adequate absorption of the subcutaneous dose, as long‑acting basal insulins require 2–4 hours to reach therapeutic plasma concentrations. 3

Continue the IV insulin infusion for 1–2 hours after the basal insulin injection to further ensure continuous insulin coverage during the absorption phase. 2, 3 Failure to overlap is the single most common error leading to DKA recurrence. 2, 3

Calculating the Basal Insulin Dose

Method 1: Based on 24‑Hour IV Insulin Requirement

• Calculate the total IV insulin delivered over the preceding 24 hours. 1
• Give 50% of that 24‑hour total as a single daily dose of long‑acting basal insulin (glargine or detemir). 1, 2
• Divide the remaining 50% equally among three meals as rapid‑acting prandial insulin (lispro, aspart, or glulisine). 1, 2

Example: If the patient received 48 units of IV insulin over 24 hours, administer 24 units of glargine subcutaneously 2–4 hours before stopping the drip, and give 8 units of rapid‑acting insulin before each meal. 1

Method 2: Weight‑Based Dosing

• For metabolically stable adults after DKA resolution, the American Diabetes Association recommends a total daily dose of 0.5 units/kg/day, with 50% as basal insulin. 4
• For patients with ongoing metabolic stress or infection, doses up to 0.65–1.0 units/kg/day may be necessary. 4

Example: A 70 kg patient would receive 17.5 units of glargine (0.5 × 70 ÷ 2) as the basal dose. 4

Monitoring During the Transition

• Check blood glucose every 2–4 hours during the overlap period and for the first 24 hours after stopping IV insulin. 1, 2
• Measure serum potassium every 2–4 hours until stable, as insulin drives potassium intracellularly and can precipitate life‑threatening hypokalemia. 2, 3
• Maintain serum potassium between 4.0–5.0 mEq/L by adding 20–30 mEq/L potassium to IV fluids once renal function is adequate. 2, 3

Critical Pitfalls to Avoid

• Never stop the IV insulin infusion without first administering basal insulin 2–4 hours earlier—this is the most frequent cause of recurrent DKA and rebound hyperglycemia. 1, 2, 4, 3
• Do not use correction‑only (sliding‑scale) insulin without basal coverage, as this approach leads to worse outcomes and higher complication rates. 4, 3
• Do not transition before complete DKA resolution (pH > 7.3, bicarbonate ≥ 18 mEq/L, anion gap ≤ 12 mEq/L, glucose < 200 mg/dL). 2, 4, 3
• Avoid premature transition if the patient cannot tolerate oral intake or is hemodynamically unstable. 3

Evidence Supporting Early Basal Insulin

A 2025 meta‑analysis of eight randomized controlled trials (468 participants) demonstrated that early subcutaneous basal insulin given concurrently with IV insulin infusion significantly accelerates DKA resolution (mean difference –4.02 hours, 95% CI –5.52 to –2.52, p < 0.001) and reduces total IV insulin requirements (mean difference –19.2 units, 95% CI –28.99 to –9.26, p < 0.001) without increasing hypoglycemia or hypokalemia risk. 5 This approach may shorten ICU length of stay and reduce treatment costs. 6, 5

Prandial and Correction Insulin

• Administer rapid‑acting insulin 0–15 minutes before each meal to cover prandial glucose excursions. 3
• For pre‑meal glucose > 250 mg/dL, add 2 units of rapid‑acting insulin to the scheduled dose. 3
• For pre‑meal glucose > 350 mg/dL, add 4 units of rapid‑acting insulin. 3
• An individualized correction dose can be calculated using the Insulin Sensitivity Factor (1500 ÷ total daily dose), then applying (current glucose – target glucose) ÷ ISF. 3

Special Considerations

• Elderly patients (> 65 years): reduce the initial subcutaneous dose by 20–50% to minimize hypoglycemia risk. 3
• Renal impairment (especially end‑stage kidney disease): reduce dose by ≈ 50% for type 2 diabetes and 35–40% for type 1 diabetes. 3
• Patients with poor oral intake: apply a 20–50% dose reduction. 3