According to US FDA, Metformin can now be safely used in patients with mild and in some cases, moderate kidney impairment after decades of warning against it.

Metformin previously had been contraindicated for patients with renal disease or dysfunction, as suggested by serum creatinine levels at or above 1.5 mg/dL for men and 1.4 mg/dL for women, or abnormal creatinine clearance.

FDA recommendations to health professionals:

1. Before starting Metformin, assess renal function using eGFR rather than blood creatinine concentration as the former also factors in the patient’s age, gender, race and/or weight.
2. Metformin is contraindicated in patients with an eGFR below 30 mL/minute/1.73 m2.
3. Starting Metformin in patients with an eGFR between 30-45 mL/minute/1.73 m2 is not recommended.
4. Obtain an eGFR at least annually in all patients taking metformin. In patients at increased risk for the development of renal impairment such as the elderly, renal function should be assessed more frequently.
5. In patients taking Metformin whose eGFR later falls below 45 mL/minute/1.73 m2, assess the benefits and risks of continuing treatment. Discontinue Metformin if the patient’s eGFR later falls below 30 mL/minute/1.73 m2.
6. Discontinue Metformin at the time of or before an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60 mL/minute/1.73 m2; in patients with a history of liver disease, alcoholism, or heart failure; or in patients who will be administered intra-arterial iodinated contrast. Re-evaluate eGFR 48 hours after the imaging procedure; restart Metformin if renal function is stable.

Source : U.S Food and Drug Administration

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