A refractometer is commonly used to estimate which property of urine?

• A. Specific Gravity
• B. pH
• C. Osmolarity
• D. Temperature

Answer: (A)

Measuring how much light bends as it passes through urine is how a refractometer works. That bending, or refractive index, rises as the solution has more dissolved particles. In urine, more solutes make it denser, so the refractive index is used to estimate urine specific gravity—the ratio of urine density to water. Specific gravity is a practical proxy for how concentrated the urine is, which helps assess hydration status and kidney concentrating ability.

pH is about hydrogen ion activity, not how light travels through liquid, so it’s measured with a pH meter or indicator strips. Osmolarity is a measure of particle concentration per liter, which is related but not directly read by a refractometer; SG can correlate with osmolarity, but the refractometer provides a specific gravity reading, not osmolarity. Temperature can influence readings, and many devices compensate for it, but the key property obtained from a refractometer in urine analysis is the specific gravity.