What initial dose of insulin glargine (Lantus) should be given to an adult whose diabetic ketoacidosis has resolved (anion gap closed) while receiving a regular insulin IV infusion at 3.6 U/hr?

Transitioning from IV Insulin to Subcutaneous Lantus After DKA Resolution

For a patient whose DKA has resolved (anion gap closed) while receiving 3.6 U/hr of IV insulin, start Lantus at approximately 43 units subcutaneously, administered 2–4 hours before discontinuing the insulin drip. 1

Calculating the Initial Lantus Dose

The total daily insulin requirement is calculated by multiplying the current IV infusion rate by 24 hours:

• 3.6 U/hr × 24 hours = 86.4 units total daily dose (TDD) 1

For the transition from IV to subcutaneous insulin, use 50% of the TDD as basal insulin (Lantus):

• 86.4 units × 0.5 = 43.2 units of Lantus once daily 1, 2

The remaining 50% (43.2 units) should be divided equally among three meals as rapid-acting prandial insulin (approximately 14 units before each meal). 1, 2

Critical Timing: The 2–4 Hour Overlap

Administer the first dose of Lantus 2–4 hours BEFORE stopping the IV insulin infusion—this overlap is mandatory to prevent rebound hyperglycemia and recurrent DKA. 3, 1, 4 Long-acting basal insulins require 2–4 hours to achieve therapeutic plasma concentrations after subcutaneous injection, and failure to overlap is the most common cause of DKA recurrence. 1

Continue the IV insulin infusion for an additional 1–2 hours after giving the Lantus dose to ensure adequate absorption and prevent a therapeutic gap. 3, 1

Verification of DKA Resolution

Before initiating this transition, confirm that all of the following criteria are met:

• Anion gap ≤12 mEq/L 3
• Serum bicarbonate ≥18 mEq/L 3
• Venous pH >7.3 3
• Glucose <200 mg/dL 3
• Patient able to tolerate oral intake 3

Prandial Insulin Coverage

In addition to Lantus, the patient requires rapid-acting insulin (lispro, aspart, or glulisine) before each meal:

• Start with 14 units before breakfast, lunch, and dinner (total 43 units prandial) 1, 2
• Administer 0–15 minutes before meals for optimal postprandial control 2, 1

Correction Insulin Protocol

Add supplemental rapid-acting insulin based on pre-meal glucose:

• Pre-meal glucose >250 mg/dL: add 2 units 2, 1
• Pre-meal glucose >350 mg/dL: add 4 units 2, 1

Monitoring After Transition

Check capillary blood glucose before each meal and at bedtime for the first 24–48 hours after transition. 3, 1 Target glucose range is 140–180 mg/dL for hospitalized patients. 2

Monitor serum potassium every 2–4 hours initially, as insulin continues to drive potassium intracellularly; maintain potassium between 4–5 mEq/L. 3, 1

Dose Adjustments for High-Risk Patients

If the patient has any of the following characteristics, reduce the initial Lantus dose by 20–50%:

• Age >65 years 1, 2
• Renal impairment (reduce by 50% in CKD stage 5) 2, 1
• Poor oral intake 1, 2

For a standard adult without these risk factors recovering from DKA, the full calculated dose of 43 units is appropriate. 1

Common Pitfalls to Avoid

Never stop the IV insulin infusion without first administering Lantus 2–4 hours earlier—this is the single most common error leading to DKA recurrence and rebound hyperglycemia. 3, 1, 4 Studies show that administering glargine during the IV insulin infusion reduces rebound hyperglycemia from 93.5% to 33.3% without increasing hypoglycemia risk. 4

Do not use sliding-scale insulin as monotherapy after stopping the IV drip—this approach is condemned by all major diabetes guidelines and leads to dangerous glucose fluctuations. 2, 1

Never give rapid-acting insulin at bedtime as a sole correction dose, as this markedly increases nocturnal hypoglycemia risk. 2, 1

Titration After Discharge

Adjust Lantus every 3 days based on fasting glucose:

• Fasting glucose 140–179 mg/dL: increase by 2 units 2
• Fasting glucose ≥180 mg/dL: increase by 4 units 2
• Target fasting glucose: 80–130 mg/dL 2

If hypoglycemia occurs without clear cause, reduce the implicated insulin dose by 10–20% immediately. 2, 1