How Safe Is Metformin in Stage 4 Chronic Kidney Disease?

Metformin is excreted renally and is contraindicated (according to U.S. prescribing information) in patients with estimated glomerular filtration rates (eGFRs) <30 mL/minute/1.73 m² to prevent lactic acidosis. However, some evidence suggests that continuing metformin below this eGFR threshold is safe and beneficial. Researchers analyzed a Scottish national database of patients with diabetes to identify those taking metformin whose chronic kidney disease progressed to stage 4 or 5 (eGFR, <30 mL/minute/1.73 m²) and who then either continued metformin for ≥6 months (≈2600 patients) or discontinued it (≈1700 patients). The researchers used a target-trial emulation study design, which can reduce — but not eliminate — residual confounding.

In adju…