**Core Concept**
Diabetes mellitus and hypertension often coexist, requiring antihypertensive therapy that minimizes the risk of hypoglycemia or exacerbating diabetic nephropathy. The choice of antihypertensive agent in diabetic patients involves careful consideration of their metabolic effects, potential for electrolyte imbalances, and impact on renal function.

**Why the Correct Answer is Right**
In diabetic patients, the ideal antihypertensive agent should not worsen glucose tolerance or increase the risk of hypoglycemia. Calcium channel blockers (CCBs), such as **amlodipine**, are a preferred choice for managing hypertension in diabetic patients. They work by inhibiting the influx of calcium ions into smooth muscle cells, leading to vasodilation and decreased peripheral resistance. CCBs do not significantly affect glucose metabolism or insulin sensitivity, making them a suitable option for diabetic patients.

**Why Each Wrong Option is Incorrect**
**Option A:**
* ACE inhibitors, such as **lisinopril**, are another good option for diabetic patients, but they can cause hyperkalemia and are not the best choice in this context.

**Option B:**
* Beta-blockers, such as **metoprolol**, are generally avoided in diabetic patients due to their potential to worsen glucose intolerance and mask hypoglycemic symptoms.

**Option C:**
* Thiazide diuretics, such as **hydrochlorothiazide**, can worsen glucose intolerance and increase the risk of hypoglycemia, making them a less favorable choice for diabetic patients.

**Clinical Pearl / High-Yield Fact**
When selecting antihypertensive therapy for diabetic patients, consider the metabolic effects of each agent and choose options that minimize the risk of hypoglycemia or exacerbating diabetic nephropathy.

**Correct Answer: C. Thiazide diuretics are generally avoided in diabetic patients due to their potential to worsen glucose intolerance and mask hypoglycemic symptoms.**