A 55-year-old man who has type 2 diabetes, obesity, hypertension, and hypercholesterolemia recently had an abnormal result on a cardiac stress test. He has stable microalbuminuria and a serum creatinine concentration of 1.2 mg/dL). He consulted a cardiologist who has scheduled a cardiac catheterization in 2 weeks. His diabetes is currently treated with metformin 1000 mg twice daily and pioglitazone 30 mg daily.

In addition to maintenance of hydration, which of the following changes, if any, should be made to the drug regimen before catheterization?

A. Make no change to his medications

B. Withhold metformin on the morning of surgery

C. Withhold pioglitazone on the morning of surgery

D. Discontinue all oral anti-diabetes medications