What are the management considerations for a patient with impaired renal function on Farxiga (dapagliflozin) and insulin regimen consisting of glargine 30 units and 8 units Humalog (insulin lispro) TID?

Management of Farxiga with Insulin in Impaired Renal Function

Critical First Step: Assess eGFR and Continue Farxiga

Continue Farxiga 10 mg daily regardless of current eGFR, as long as eGFR ≥25 mL/min/1.73 m² and the patient is not on dialysis. 1 Once initiated, dapagliflozin should be continued even if eGFR falls below the initiation threshold of 45 mL/min/1.73 m² for glycemic control, because cardiovascular and renal protective benefits persist at lower eGFR levels. 1, 2

Insulin Dose Adjustment Algorithm

Reduce total daily insulin dose by approximately 20% when Farxiga is active to prevent hypoglycemia. 1

Specific Adjustments for This Regimen:

• Glargine: Reduce from 30 units to 24 units daily 1
• Humalog: Reduce from 8 units TID to 6 units TID (or maintain 8 units but monitor closely) 1
• Monitor glucose closely for the first 4 weeks, especially before meals and at bedtime 1

Critical Safety Point:

Maintain at least low-dose insulin even if glucose improves significantly—never discontinue insulin completely in insulin-requiring patients on SGLT2 inhibitors, as this dramatically increases risk of euglycemic diabetic ketoacidosis. 1, 2, 3

Renal Function Monitoring Protocol

• Check eGFR within 1-2 weeks after any insulin dose adjustment or if clinical status changes 1, 2
• Expect a transient eGFR dip of 3-5 mL/min/1.73 m² within the first 1-4 weeks of Farxiga therapy—this is hemodynamic, reversible, and does not require drug discontinuation 1, 2, 3
• If eGFR decreases >30% from baseline AND patient shows signs of hypovolemia, assess volume status and consider reducing any concurrent diuretics before adjusting Farxiga 1, 2
• Continue monitoring eGFR every 3-6 months if eGFR 45-59 mL/min/1.73 m², or at least annually if eGFR ≥60 mL/min/1.73 m² 1, 2

Sick Day Protocol (Non-Negotiable Patient Education)

Instruct the patient to STOP Farxiga immediately during any acute illness, especially with fever, vomiting, diarrhea, or reduced oral intake. 1, 2, 3

Specific Instructions:

• Hold Farxiga at least 3 days before major surgery or procedures requiring prolonged fasting 1, 2, 3
• Continue at least low-dose insulin during illness—do not stop insulin even when Farxiga is held 1, 2, 3
• Check blood or urine ketones if patient develops nausea, vomiting, or malaise, even if glucose is 150-250 mg/dL (euglycemic DKA can occur) 1, 2
• Resume Farxiga only after full recovery and normal oral intake is re-established 2, 3

Volume Status and Hypotension Management

• Assess for signs of volume depletion before each visit: orthostatic hypotension, dizziness, weakness 1
• If patient is on loop or thiazide diuretics, consider reducing diuretic dose proactively to prevent excessive volume depletion when Farxiga is active 1, 2
• Educate patient on symptoms of dehydration and instruct them to hold Farxiga if unable to maintain adequate oral fluid intake 1, 2

Genital Mycotic Infection Prevention

• Counsel on daily genital hygiene measures to reduce risk of mycotic infections, which occur in approximately 6% of patients on SGLT2 inhibitors versus 1% on placebo 1, 2
• Advise patient to report any genital discomfort, discharge, or urinary symptoms promptly 1, 2

Common Pitfall to Avoid

Do not discontinue Farxiga solely because eGFR falls below 45 mL/min/1.73 m²—the cardiovascular and renal protective benefits remain robust even when glycemic efficacy diminishes at lower eGFR levels. 1, 2 The only absolute contraindication is eGFR <25 mL/min/1.73 m² for initiation (but continuation is reasonable if already on therapy) or initiation of dialysis. 1, 4

When to Reassess the Regimen

• If HbA1c remains elevated despite this regimen, consider adding a GLP-1 receptor agonist (if eGFR ≥30 mL/min/1.73 m²) rather than increasing insulin doses excessively 1
• If eGFR falls below 25 mL/min/1.73 m², continue Farxiga 10 mg daily until dialysis is initiated, but shift glycemic management strategy toward insulin optimization and consider GLP-1 RA if eGFR ≥30 mL/min/1.73 m² 1, 2