In conclusion, with a CrCl of 23 ml/min, metformin is contraindicated and should be discontinued, with alternative diabetes medications considered based on the patient's specific needs and comorbidities. Metformin is generally not recommended for individuals with an eGFR below 30 mL/min/1.73m², as this indicates severe kidney impairment. In such cases, metformin is considered contraindicated. Continuing metformin with an eGFR below this level significantly increases the risk of drug accumulation. When the FDA approved metformin in 1994, they attached a boxed warning that cautioned against use of the drug in people who had even the slightest bit of abnormal kidney function, that is, men who had serum creatinine at or above 1.5 mg/dL and women who had serum creatinine at or above 1.4 mg/dL. eGFR 30 mL/min/1.73 : stop treatment with metformin renal risk: Use with caution if there is a risk of rapid deterioration in renal function (e.g., dehydration, infection). They note that any specific value of serum creatinine concentration chosen as a cut-off point for prescribing metformin will be arbitrary because of variations in muscle mass and protein turnover. Metformin is safe in patients with an eGFR above 45 mL per minute per 1.73 m 2 unless risk for acute kidney injury is high. Currently, the contraindication for metformin use in patients with renal insufficiency is rigidly defined as a serum creatinine level of 1.5 mg/dL or higher in men and 1.4 mg/dL or higher in women. Today’s U.S. Food and Drug Administration prescribing guidelines for metformin contraindicate its use in men and women with serum creatinine concentrations ≥1.5 and ≥1.4 mg/dL (≥132 and ≥123 µmol/L), respectively. No, metformin should not be used in a person with a creatinine clearance of 25 mL/min/1.73 m² as this represents severe renal impairment (Stage 4 CKD), and metformin is absolutely contraindicated at this level of kidney function. 1 Can I take metformin if I have mild kidney disease? Yes, you can take metformin in mild kidney disease. Usually, no metformin dose adjustment is needed, but monitor kidney function regularly. What if my eGFR is below 30? According to the metformin eGFR guideline, it should be avoided below 30 eGFR. Your doctor will choose an alternative.