Is it safe to take metformin (Metformin) with impaired renal function, specifically a creatinine level indicative of mild kidney dysfunction and a Glomerular Filtration Rate (GFR) of 70?

From the Guidelines

With a creatinine level of 1.32 and a GFR of 70, it is generally considered safe to take metformin, as the most recent and highest quality study suggests that metformin can be safely used in people with an estimated glomerular filtration rate ≥30 mL/min/1.73 m² 1.

Key Considerations

• Metformin is typically safe for patients with a GFR above 45 ml/min, and a GFR of 70 falls within the acceptable range for standard dosing 1.
• However, it is essential to monitor kidney function regularly, typically every 3-6 months, as kidney function can change over time 1.
• The risk of lactic acidosis, a rare but serious side effect, is increased when GFR falls below 30 ml/min, but this is not a concern with a GFR of 70 1.
• To minimize gastrointestinal side effects, metformin should be taken with meals, and the dose should not be adjusted without consulting a healthcare provider 1.

Monitoring and Dose Adjustments

• According to the KDIGO 2022 clinical practice guideline, patients with a GFR of 70 do not require dose adjustments, but kidney function should be monitored at least annually or every 3-6 months 1.
• Vitamin B12 levels should also be monitored, especially if metformin is used for more than 4 years, due to the increased risk of vitamin B12 deficiency 1.

Important Warnings

• If symptoms like unusual muscle pain, trouble breathing, stomach discomfort, dizziness, or extreme fatigue occur while taking metformin, medical attention should be sought immediately, as these could indicate lactic acidosis 1.

From the FDA Drug Label

Metformin hydrochloride tablets are contraindicated in patients with an eGFR less than 30 mL/min/1.73 m 2 Initiation of metformin hydrochloride tablets is not recommended in patients with eGFR between 30 to 45 mL/min/1. 73 m 2. Obtain an eGFR at least annually in all patients taking metformin hydrochloride tablets. In patients taking metformin hydrochloride tablets whose eGFR falls below 45 mL/min/1. 73 m 2, assess the benefit and risk of continuing therapy.

The patient's GFR of 70 is above the threshold where metformin is contraindicated or not recommended. Key considerations for this patient include:

• Renal function: The patient's eGFR is 70 mL/min/1.73 m^2, which is above the threshold for contraindication or caution.
• Monitoring: The patient's eGFR should be monitored at least annually, as recommended for all patients taking metformin. Based on the information provided, it appears that it is safe to take metformin with a creatinine level of 1.32 and a GFR of 70, as the patient's renal function is not severely impaired 2.

From the Research

Metformin Safety with Elevated Creatinine Levels

• The safety of taking metformin with a creatinine level of 1.32 and a GFR of 70 is a concern, as metformin is contraindicated in patients with significant renal impairment 3, 4.
• A study published in the Journal of the American Society of Nephrology found that renal function equations may not accurately predict renal function in patients with chronic kidney disease and normal serum creatinine levels, highlighting the need for careful monitoring of renal function in patients taking metformin 4.
• Another study published in The Journal of Clinical Endocrinology and Metabolism compared the efficacy and safety of pioglitazone versus metformin in patients with type 2 diabetes mellitus, and found that metformin was associated with a decrease in body weight and a reduction in LDL cholesterol, but did not provide specific guidance on the safety of metformin with elevated creatinine levels 5.
• A study published in Diabetes Care found that the addition of pioglitazone or metformin to sulfonylurea therapy in patients with inadequately controlled type 2 diabetes resulted in similar improvements in glycemic control, but did not address the safety of metformin with elevated creatinine levels 6.
• A recent study published in The Pan African Medical Journal found that every unit increase in creatinine level was linked to a 10% increased odds of kidney dysfunction in patients with type 2 diabetes mellitus, highlighting the importance of monitoring creatinine levels in patients taking metformin 7.

Renal Function and Metformin

• The Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) classification of kidney function is an important tool for assessing renal function in patients with type 2 diabetes mellitus 7.
• Patients with a GFR of 70 and a creatinine level of 1.32 should be carefully monitored for signs of renal impairment, as metformin may worsen renal function in patients with significant renal impairment 3, 4.
• The use of metformin in patients with elevated creatinine levels should be approached with caution, and patients should be closely monitored for signs of renal impairment, such as a decrease in GFR or an increase in creatinine levels 4, 7.