Metformin Should Be Discontinued in Hospitalized Patients with Type 2 Diabetes
Metformin should be discontinued in hospitalized patients with type 2 diabetes due to increased risk of lactic acidosis in acute illness settings, especially in patients with conditions that may compromise renal function, cause tissue hypoxia, or impair lactate clearance. 1
Rationale for Discontinuing Metformin in Hospitalized Patients
Risk of Lactic Acidosis
- Hospitalized patients often have conditions that increase the risk of lactic acidosis, including:
- A study from China showed inpatient metformin use was associated with increased incidence of lactic acidosis (adjusted hazard ratio 4.46,95% CI 1.11–18.0) in patients with COVID-19 1
- Higher doses, worse kidney function, and greater illness severity were associated with lactic acidosis risk 1
Specific Conditions Requiring Metformin Discontinuation
- Acute kidney injury or eGFR <30 mL/min/1.73 m² 1, 2
- Hypoxic states 1
- Shock or hemodynamic instability 1
- Before iodinated contrast procedures 1
- Liver failure 1
- Alcoholism 1
- Acute heart failure 1
Alternative Inpatient Glycemic Management
Insulin-Based Regimens
- Insulin is the preferred treatment for hyperglycemia in most hospitalized patients 1
- For patients who are eating:
- Basal-bolus insulin regimen is recommended 1
- For fasting patients or those undergoing procedures:
- Basal-plus approach (basal insulin with correctional doses) 1
- For patients with good glycemic control on oral agents at home:
- Sliding scale insulin alone may be sufficient 1
Special Considerations
Heart Failure Patients
- In patients with stable heart failure, metformin may be continued if eGFR remains >30 mL/min/1.73 m², but should be avoided in unstable or hospitalized heart failure patients 1
Monitoring Requirements
- Lactate concentrations should be measured in fragile patients 1
- Kidney function should be reassessed before restarting metformin after hospitalization 1
Emerging Evidence and Controversies
- A recent observational cohort study (2025) found that continuation of metformin during hospitalization was associated with decreased risk of post-hospitalization insulin prescriptions, hypoglycemia, readmissions, and mortality 3
- This emerging evidence questions traditional recommendations to hold metformin during hospitalization 3
- However, this study was observational and may have selection bias, with healthier patients more likely to have metformin continued 3
Restarting Metformin After Hospitalization
- Reassess kidney function before restarting metformin 1
- Ensure resolution of acute conditions that increase lactic acidosis risk 1
- Consider dose reduction if eGFR is 30-45 mL/min/1.73 m² 1
- Do not restart if eGFR remains <30 mL/min/1.73 m² 1
Common Pitfalls in Inpatient Metformin Management
- Failure to recognize conditions that increase lactic acidosis risk 1
- Continuing metformin before contrast studies 1
- Inadequate monitoring of renal function in at-risk patients 1
- Restarting metformin too early after acute illness 1
Despite some emerging evidence suggesting potential benefits of continuing metformin in select hospitalized patients, current guidelines still recommend discontinuation in most inpatient settings due to safety concerns related to lactic acidosis risk in acute illness.