A patient with type 1 diabetes is taking NPH insulin, 30 units every day. A nurse notes that the patient is also taking metoprolol [Lopressor]. What education should the nurse provide to the patient?
a. "Metoprolol has no effect on diabetes mellitus or on your insulin requirements."
b. "Metoprolol interferes with the effects of insulin, so you may need to increase your insulin dose."
c. "Metoprolol may mask signs of hypoglycemia, so you need to monitor your blood glucose closely."
d. "Metoprolol may potentiate the effects of the insulin, so the dose should be reduced."