How does needle gauge relate to diameter?

• A. Lower gauge (smaller number) corresponds to a larger diameter
• B. Higher gauge (larger number) corresponds to a larger diameter
• C. Gauge and diameter are unrelated
• D. Diameter decreases as gauge decreases

Answer: (A)

Needle gauge uses an inverse scale: the smaller the gauge number, the thicker the needle and the larger the bore diameter. As the gauge number increases, the needle becomes thinner and the bore diameter decreases. For example, an 18-gauge needle has a larger bore than a 22-gauge needle, which is why it’s often chosen when rapid fluid administration is needed. This relationship matters in practice because it balances flow rate with tissue trauma: thicker needles allow faster flow but can cause more tissue damage, while thinner needles are gentler but slower for large volumes.

The other statements don’t fit because a higher gauge does not mean a larger diameter, gauge and diameter are not unrelated, and saying diameter decreases as gauge decreases contradicts the established inverse relationship.