A 62-year-old man with type 2 diabetes and CKD stage 3b (eGFR 38 mL/min/1.73m2) is on metformin. His physician is concerned about metformin's risk in this situation. At which eGFR threshold is metformin absolutely contraindicated as per current guidelines?

• A eGFR < 60 mL/min/1.73m2
• B eGFR < 30 mL/min/1.73m2 ✓
• C eGFR < 45 mL/min/1.73m2
• D eGFR < 15 mL/min/1.73m2

Explanation

According to FDA and current KDIGO/ADA guidelines, metformin is contraindicated when eGFR falls below 30 mL/min/1.73m2 (Stage 4-5 CKD). Between eGFR 30-45, it should be used with caution and dose reduction, and initiated cautiously only above eGFR 45. The risk at low GFR is lactic acidosis, as metformin accumulates when renal clearance is impaired and inhibits hepatic lactate uptake. At eGFR 38 (as in this case), metformin can be continued with monitoring and reduced dose, not absolutely discontinued.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.