Which condition is a major contraindication to metformin therapy?

• A. eGFR less than 30 mL/min/1.73 m2
• B. Controlled hypertension
• C. Vitamin D sufficiency
• D. No liver disease

Answer: (A)

Metformin safety hinges on kidney function because the drug is cleared by the kidneys. When the eGFR is less than 30 mL/min/1.73 m2, metformin can build up in the body, increasing the risk of lactic acidosis, a serious and potentially deadly complication. That makes this level of renal impairment a major contraindication to metformin therapy.

The other options don’t pose the same safety barrier. Controlled hypertension on its own doesn’t contraindicate metformin, since kidney function is the key factor. Vitamin D sufficiency has no direct bearing on metformin use, and having no liver disease removes a different risk factor rather than creating one, so it isn’t a contraindication.