**Core Concept**
Insulin and certain medications can cause hypoglycemia by promoting excessive glucose uptake or inhibiting glucose release from storage sites. The question tests the student's ability to identify substances that do not cause hypoglycemia, highlighting the importance of understanding the mechanisms of glucose regulation.

**Why the Correct Answer is Right**
The correct answer is a substance that either does not increase insulin levels or does not promote glucose uptake. For example, glucagon has a counter-regulatory effect on glucose metabolism, increasing blood glucose levels by stimulating glycogenolysis and gluconeogenesis. This action prevents hypoglycemia.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because insulin is a well-known cause of hypoglycemia due to its role in promoting glucose uptake in cells.
**Option B:** Incorrect because sulfonylureas stimulate insulin release from pancreatic beta cells, leading to hypoglycemia.
**Option C:** Incorrect because metformin can cause hypoglycemia, especially when used in combination with other antidiabetic medications.

**Clinical Pearl / High-Yield Fact**
The counter-regulatory hormones, including glucagon, cortisol, and epinephrine, play a crucial role in preventing hypoglycemia by promoting glucose release from storage sites.

**Correct Answer:** D. Glucagon