Is adjusting Lantus (insulin glargine) from 20 units to 18 units and adding an SGLT2 inhibitor (e.g., Canagliflozin) 25 mg po daily appropriate for managing hypoglycemia?

Adjusting Lantus and Adding Jardiance for Fasting Hypoglycemia

Yes, reducing Lantus from 20 to 18 units and adding Jardiance (canagliflozin) 25 mg daily is appropriate for a patient with fasting glucose of 60-100 mg/dL, but the Lantus dose should be reduced by at least 20% (to 16 units or lower) when adding an SGLT2 inhibitor to prevent hypoglycemia. 1, 2

Rationale for Dose Adjustment

The current fasting glucose range of 60-100 mg/dL indicates the patient is already at or below target (80-130 mg/dL), with values at 60 mg/dL representing hypoglycemia. 3 This necessitates immediate basal insulin reduction before adding any glucose-lowering medication.

Why a Larger Reduction is Needed

• When adding SGLT2 inhibitors to insulin regimens, the insulin dose typically requires reduction to prevent hypoglycemia, with guidelines recommending dose reductions when baseline glucose is already controlled. 1
• A 10% reduction (from 20 to 18 units) may be insufficient given that fasting glucose is already reaching 60 mg/dL, which represents frank hypoglycemia requiring a 10-20% dose reduction. 3
• The FDA label for insulin glargine explicitly states that dosage reductions and increased glucose monitoring are required when coadministered with SGLT2 inhibitors due to increased hypoglycemia risk. 2

Recommended Adjustment Algorithm

Step 1: Reduce Lantus Immediately

• Decrease Lantus to 16 units (20% reduction) given current fasting glucose values include hypoglycemic readings at 60 mg/dL. 3
• If fasting glucose consistently runs 80-100 mg/dL without values <70 mg/dL, a 10-15% reduction (to 17-18 units) may be acceptable. 3

Step 2: Initiate Jardiance

• Start canagliflozin 25 mg once daily in the morning. 4
• SGLT2 inhibitors should be temporarily stopped during acute illness with volume depletion (vomiting, diarrhea, decreased fluid intake) to prevent diabetic ketoacidosis. 1

Step 3: Intensive Monitoring

• Monitor fasting blood glucose daily for the first 2-3 weeks after medication changes. 3
• Check for ketones if blood glucose exceeds 250 mg/dL, as SGLT2 inhibitors increase ketoacidosis risk even with modest hyperglycemia. 1
• Reassess Lantus dose every 3 days based on fasting glucose patterns, increasing by 2 units if fasting glucose is 140-179 mg/dL or by 4 units if ≥180 mg/dL. 3

Critical Safety Considerations

Hypoglycemia Prevention

• If more than 2 fasting glucose values per week are <80 mg/dL, decrease Lantus by an additional 2 units. 3
• Patients should be educated on hypoglycemia recognition and treatment, particularly during the first month of combined therapy. 3

SGLT2 Inhibitor-Specific Risks

• Genital mycotic infections occur in 11-15% of women and 8-9% of men taking canagliflozin. 4
• Urinary tract infections increase slightly (5-7% vs 4% with placebo). 4
• Volume depletion and postural hypotension may occur, particularly in elderly patients or those on diuretics. 4
• Canagliflozin increases LDL cholesterol by approximately 8% compared to placebo. 4

Sick Day Management

• During acute illness with vomiting, diarrhea, or decreased oral intake, temporarily stop canagliflozin and reduce insulin doses if hypoglycemia occurs. 1
• Resume medications at usual doses within 24-48 hours of normal eating and drinking, or seek medical assistance if symptoms persist beyond 72 hours. 1

Common Pitfalls to Avoid

• Failing to reduce insulin adequately when adding SGLT2 inhibitors leads to increased hypoglycemia risk. 1, 2
• Ignoring fasting glucose values at 60 mg/dL as "acceptable" when they represent true hypoglycemia requiring immediate dose reduction. 3
• Not educating patients about sick day medication management, particularly the need to temporarily stop SGLT2 inhibitors during acute illness. 1
• Continuing to escalate basal insulin if postprandial hyperglycemia develops, rather than adding prandial insulin or GLP-1 receptor agonists. 1, 3

Alternative Consideration

If the patient has established cardiovascular disease, heart failure, or chronic kidney disease, verify that canagliflozin is the optimal SGLT2 inhibitor choice, as empagliflozin and dapagliflozin have more robust cardiovascular outcome data. 1 However, all SGLT2 inhibitors demonstrate similar glucose-lowering efficacy and hypoglycemia risk when combined with insulin. 1