What is a major contraindication for prescribing metformin?

The major contraindication for prescribing metformin is renal failure. This is primarily due to the way metformin is eliminated from the body. Metformin is predominantly excreted unchanged by the kidneys; therefore, in patients with renal impairment, the risk of accumulating the drug increases significantly. This accumulation can lead to a severe condition known as lactic acidosis, which is a serious and potentially life-threatening complication associated with metformin usage.

When renal function declines, the clearance of the drug diminishes, which in turn raises the serum levels of metformin. Because lactic acidosis can occur when lactic levels rise due to impaired clearance paired with metformin's effects, it is crucial to assess renal function before initiating therapy with this medication.

Although cardiac failure and hepatic failure also present concerns for metformin use, current guidelines do not explicitly list them as absolute contraindications in the same way renal failure is. For instance, caution is advised in cases of congestive heart failure (CHF), particularly if it is severe, as it may lead to renal impairment, which then affects metformin clearance. However, the primary concern for prescribing metformin relates to renal function, making renal failure the major contraindication.

Gastric failure is not considered a direct contraind