**Core Concept:** Diabetic ketoacidosis is a life-threatening emergency characterized by hyperglycemia, ketonemia, and ketonuria, often in a patient with poorly controlled diabetes mellitus. It is a clinical syndrome caused by relative insulin deficiency due to beta-cell dysfunction.

**Why the Correct Answer is Right:** In this scenario, the patient presents with low blood pressure (80/50) and polyuria (infrequent urination), which are classic features of diabetic ketoacidosis. The doctor prescribes a medicine known as insulin, which addresses the underlying cause of the patient's symptoms. Insulin is a hormone produced by the beta cells of the pancreas that promotes glucose uptake in cells, reduces gluconeogenesis, and enhances glycogen synthesis, ultimately leading to improved blood glucose levels and alleviation of diabetic ketoacidosis symptoms.

**Why Each Wrong Option is Incorrect:**

A. While the patient's blood glucose level is high, the correct treatment is insulin, not oral hypoglycemic agents like Metformin (Option A). Metformin is a biguanide used for the treatment of type 2 diabetes mellitus, not for diabetic ketoacidosis.

B. Diabetic ketoacidosis treatment focuses on addressing the underlying cause (insulin deficiency) rather than a medication that improves blood pressure, like ACE inhibitors (Option B).

C. Calcium channel blockers (CCBs) like nifedipine are used for hypertension management, not for treating diabetic ketoacidosis (Option C).

D. While the patient's blood glucose level is high, the correct treatment is insulin, not glucocorticoids like hydrocortisone (Option D). Glucocorticoids like hydrocortisone are used for treating inflammation, stress, or hypovolemic shock, not for diabetic ketoacidosis.

**Clinical Pearl:**

Diabetic ketoacidosis is a severe complication of poorly controlled diabetes mellitus. Its management involves prompt insulin administration to correct the insulin deficiency and restore euglycemia, while maintaining adequate hydration and electrolyte replacement. In this case, the correct answer is insulin (Option D) as it addresses the primary cause of diabetic ketoacidosis (insulin deficiency) and helps to prevent complications such as cerebral edema, seizures, and coma.