**Question:** The most common route of administration of insulin is:

A. Intradermal injection
B. Subcutaneous injection
C. Intramuscular injection
D. Intravenous injection

**Correct Answer:** **B. Subcutaneous injection**

**Core Concept:** Insulin is a hormone produced by the pancreas that helps regulate blood glucose levels by facilitating glucose uptake into cells, particularly in the liver, muscles, and adipose tissue.

**Why the Correct Answer is Right:** Insulin is administered subcutaneously because it allows for a gradual release of insulin into the bloodstream, leading to stable blood glucose levels. Subcutaneous injection ensures that insulin is distributed under the skin, where it can be absorbed into the blood vessels and reach the target tissues for their glucose uptake.

**Why Each Wrong Option is Incorrect:**

A. Intradermal injection: Insulin is not absorbed efficiently through the skin layers, making this route less effective for achieving stable blood glucose levels.

C. Intramuscular injection: Insulin is not well-absorbed from muscle tissue due to the presence of connective tissue and muscle cells, which slow down the absorption process.

D. Intravenous injection: Insulin is rapidly cleared from the bloodstream when administered intravenously, leading to unstable blood glucose levels, which contradicts the intended effect of insulin therapy.

**Clinical Pearl:** Insulin administration is a crucial aspect of diabetes management, and the correct route ensures optimal blood glucose control. Subcutaneous injections using an insulin pen or syringe and needle are popular methods for administering insulin, as they provide consistent dosing and minimize the risk of insulin precipitation or contamination.