What common lab test is used to assess hydration status?

The common lab test used to assess hydration status is serum osmolality or serum electrolytes. These tests measure the concentration of solutes in the blood, which can provide direct insights into a person's hydration level.

When the body is adequately hydrated, serum osmolality typically falls within a certain range, as the balance of water and solutes remains stable. A higher serum osmolality indicates dehydration, as it reflects a concentration of solutes relative to water. In the context of hydration, serum electrolytes such as sodium and potassium can also give important information; for instance, elevated sodium levels can indicate inadequate fluid intake or excess fluid loss.

While other tests like complete blood count, urine analysis, and coagulation profiles provide valuable information for various health conditions, they are not primarily focused on assessing hydration status. Complete blood counts are generally used to evaluate the overall health of an individual and detect disorders such as anemia or infection. Urine analysis provides insights into kidney function and other conditions, but it is not a direct measure of hydration like serum osmolality and electrolytes. Coagulation profiles are more concerned with blood clotting mechanisms than with fluid balance. Therefore, serum osmolality or serum electrolytes is the most relevant option for evaluating