Which laboratory finding is commonly associated with dehydration?

• A. Elevated hemoglobin and hematocrit.
• B. Increased serum osmolarity.
• C. Increased urine specific gravity.
• D. Increased serum glucose.

Answer: (A)

Dehydration causes a drop in circulating blood volume, so the blood becomes more concentrated. With less plasma water, the concentration of red blood cells increases, leading to higher hemoglobin and hematocrit values. This hemoconcentration is a classic, reliable sign of fluid deficit. Other findings can accompany dehydration—such as higher serum osmolality or more concentrated urine (higher urine specific gravity)—but the rise in red cell concentration best reflects the reduced plasma volume. Increased serum glucose is not a specific dehydration marker and can be influenced by other factors like stress or diabetes.