When to Start Lantus in DKA
Start Lantus (insulin glargine) 1-3 hours before discontinuing the IV insulin infusion, once the patient's DKA has resolved (anion gap closed, bicarbonate >15 mmol/L, pH >7.3) and they are able to eat. 1
Timing the Transition from IV to Subcutaneous Insulin
The critical principle is overlap: subcutaneous basal insulin must be administered while IV insulin is still running to prevent rebound hyperglycemia and recurrent ketoacidosis. 1, 2
Key Steps for Transition:
Wait for DKA resolution before initiating the transition. Resolution is defined as: 1
- Glucose between 150-200 mg/dL (your patient at 270 mg/dL needs further glucose control)
- Anion gap closed
- Bicarbonate >15 mmol/L
- Venous pH >7.3
Administer Lantus 1-3 hours before stopping IV insulin to allow time for subcutaneous absorption and prevent the gap in insulin coverage that leads to rebound hyperglycemia. 2, 3
Continue IV insulin infusion for at least 1-3 hours after giving Lantus because glargine has a delayed onset of action (approximately 2-4 hours to reach therapeutic levels). 4, 2
Dosing Recommendations
Initial Lantus dose: 0.4-0.5 units/kg/day administered as a single daily dose. 3, 5
For your 67-year-old patient, if she weighs approximately 70 kg, this translates to 28-35 units of Lantus once daily.
Additional Insulin Coverage:
Add rapid-acting insulin (glulisine, lispro, or aspart) before meals once the patient can eat, starting at approximately 4-6 units per meal or using a carbohydrate ratio of 1:10-1:15. 2
This basal-bolus regimen (glargine + rapid-acting analog) is superior to NPH + regular insulin after DKA resolution, with significantly lower hypoglycemia rates (15% vs 41%, p=0.03). 2
Important Clinical Pitfalls
Do NOT Stop IV Insulin Abruptly:
The most common error is discontinuing IV insulin immediately after giving subcutaneous insulin, which creates a dangerous insulin-free period leading to: 1, 2
- Rebound hyperglycemia
- Recurrent ketoacidosis
- Prolonged hospitalization
Monitor Potassium Closely:
Early glargine administration during DKA treatment is associated with increased risk of hypokalemia (OR 3.4,95% CI 1.7-7.0). 3 Ensure potassium is maintained between 4-5 mmol/L throughout the transition. 1
Current Blood Glucose Still Too High:
Your patient's current glucose of 270 mg/dL on IV insulin suggests DKA is not yet fully resolved. Continue IV insulin until glucose reaches 150-200 mg/dL range before considering the transition. 1
Monitoring During Transition
- Check blood glucose every 2-4 hours after starting Lantus until stable. 1
- Verify DKA resolution parameters (pH, bicarbonate, anion gap) before stopping IV insulin. 1
- Ensure adequate oral intake before transitioning, as the patient needs to be able to eat to match prandial insulin coverage. 1
Evidence Quality Note
The recommendation for 1-3 hour overlap comes from the highest quality recent evidence: a 2009 randomized controlled trial demonstrating that glargine-based regimens after DKA resolution result in superior safety profiles compared to NPH-based regimens. 2 This is further supported by pediatric data showing safe co-administration practices. 3 The 2025 ADA guidelines emphasize continuing IV insulin until the patient can eat and maintaining overlap during transition. 1