Can metformin (biguanide oral hypoglycemic) be continued in an inpatient setting with stable renal function and no contraindications?

From the Guidelines

Metformin can typically be continued in the inpatient setting for patients with stable renal function and no contraindications, as long as the estimated glomerular filtration rate (eGFR) exceeds 30 mL/min/1.73m², as supported by recent studies 1.

Key Considerations for Metformin Use in Inpatient Settings

• Metformin should be maintained at the patient's usual outpatient dose, which commonly ranges from 500-1000 mg twice daily.
• Temporary discontinuation is recommended 48 hours before and after procedures involving iodinated contrast media due to the risk of contrast-induced nephropathy and subsequent lactic acidosis.
• Metformin should also be held if the patient develops acute kidney injury, hypoxemia, sepsis, or requires surgery under general anesthesia, as these conditions increase the risk of lactic acidosis.
• Regular monitoring of renal function is essential during hospitalization, with discontinuation recommended if eGFR falls below 30 ml/min/1.73m².

Rationale for Continuing Metformin

• Continuing metformin in appropriate inpatients maintains glycemic control, prevents hyperglycemia, and avoids unnecessary medication changes that could complicate the transition back to outpatient care.
• The medication works by decreasing hepatic glucose production and improving insulin sensitivity without causing hypoglycemia when used as monotherapy.

Important Safety Precautions

• Patients with a history of diabetes mellitus, compromised renal function, or those taking metformin should have their renal function checked prior to contrast agent administration, as indicated by guidelines 1.
• Metformin should be discontinued at the time of the procedure and withheld for 48 h after the procedure if intravenous contrast agent is administered, with reinstitution dependent on renal function assessment 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 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. Initiation of metformin hydrochloride tablets is not recommended in patients with eGFR between 30 to 45 mL/min/1. 73 m 2

Continuation of Metformin in Inpatient Setting:

• The patient has stable renal function and no contraindications,
• The eGFR is not less than 30 mL/min/1.73 m 2 and not between 30 to 45 mL/min/1.73 m 2,
• Then metformin can be continued in an inpatient setting 2. Key Considerations:
• Monitor renal function at least annually in all patients taking metformin hydrochloride tablets 2
• Assess the benefit and risk of continuing therapy if the eGFR falls below 45 mL/min/1.73 m 2 2
• Discontinue metformin hydrochloride tablets if the patient's eGFR later falls below 30 mL/minute/1.73 m 2 2

From the Research

Metformin Use in Inpatient Setting

• Metformin can be continued in an inpatient setting with stable renal function and no contraindications, as suggested by a study published in 2020 3.
• The study found that metformin was associated with goal glycemic levels in hospitalized patients with no adverse outcomes.
• However, it is essential to evaluate renal function prior to continuing metformin in an inpatient setting, as impaired renal function can lead to the accumulation of metformin and increase the risk of lactic acidosis 4.

Renal Function and Metformin Use

• A study published in 2014 found that metformin can be used safely in patients with mild to moderate chronic kidney disease (estimated glomerular filtration rates, 30-60 mL/min per 1.73 m2) 5.
• The Korean Diabetes Association and the Korean Society of Nephrology consensus statement suggests that metformin can be used safely when the estimated glomerular filtration rate (eGFR) is ≥45 mL/min/1.73 m² 6.
• However, metformin is contraindicated when the eGFR is <30 mL/min/1.73 m², and metformin treatment should not be started if the eGFR is between 30 and 44 mL/min/1.73 m² 6.

Guidelines for Metformin Use

• A review of guidelines and proposals for metformin withdrawal around the world found that the criteria for metformin withdrawal vary, but most guidelines suggest a threshold for withdrawing metformin based on serum creatinine or estimated glomerular filtration rate 7.
• The consensus statement from the Korean Diabetes Association and the Korean Society of Nephrology provides guidelines for metformin use in patients with diabetes and chronic kidney disease, including recommendations for metformin dose and renal function evaluation 6.