American Board of Internal Medicine (ABIM) Certification Practice Exam

The FDA recommends the initiation of metformin in patients only if their estimated GFR is greater than what value?

1. 60 mL/min/1.73 m2

2. 50 mL/min/1.73 m2

3. 45 mL/min/1.73 m2

4. 40 mL/min/1.73 m2

The correct answer is: 45 mL/min/1.73 m2

The correct answer is that the FDA recommends the initiation of metformin in patients only if their estimated GFR is greater than 45 mL/min/1.73 m². This is based on the understanding that metformin is primarily eliminated through the kidneys, and its use in patients with significantly reduced renal function can lead to an increased risk of lactic acidosis, a serious and potentially life-threatening condition. By establishing a threshold of 45 mL/min/1.73 m², the FDA aims to ensure that patients have adequate kidney function to safely metabolize and excrete metformin, thus minimizing the risk of adverse effects associated with its accumulation in cases of renal impairment. Guidelines indicate that as long as the GFR is at or above this value, metformin can be beneficial for glycemic control in patients with type 2 diabetes. Setting the threshold higher, such as at 50, 60, or 40 mL/min/1.73 m², may unnecessarily restrict the use of metformin in patients who can still tolerate the medication safely. Therefore, the determination of 45 mL/min/1.73 m² strikes a balance between maximizing treatment options for patients with diabetes while still prioritizing their safety concerning