Diabetes mellitus is characterized by which of the following?

• A. It is caused by excessive insulin production.
• B. It is defined by low blood sugar despite insulin.
• C. Lack of insulin secretion or insulin resistance impairing metabolism of carbohydrates, fats, and proteins.
• D. It affects only the elderly.

Answer: (C)

Diabetes mellitus happens when insulin isn’t doing its job—either the body doesn’t make enough insulin, or the body’s cells don’t respond to it properly. That insulin action is what allows glucose to move into cells and be used for energy. When insulin is deficient or ineffective, metabolism of carbohydrates, fats, and proteins is impaired, leading to high blood glucose levels. This description fits both major forms: insufficient insulin production and insulin resistance.

The other statements don’t fit diabetes. Too much insulin would lower blood glucose, which isn’t how diabetes is characterized. Low blood sugar despite insulin describes hypoglycemia rather than diabetes. And diabetes can affect people at any age, not just the elderly.