Which objective sign indicates dehydration in an older adult?

• A. Hematuria
• B. Increased urine output
• C. High creatinine levels
• D. Postural hypotension

Answer: (C)

Dehydration lowers circulating volume and kidney perfusion, so the kidneys conserve water and filtration drops. That reduced filtration lets waste products build up in the blood, and creatinine—a waste product from muscle metabolism that the kidneys normally clear—rises when kidney function declines. In older adults, who often have diminished kidney mass and function, even modest dehydration can noticeably increase creatinine levels, making it a reliable objective sign.

Hematuria points to blood in the urine from infection, stones, or trauma, not dehydration. Increased urine output runs contrary to dehydration, which typically causes one to produce less urine. Postural hypotension can occur with dehydration but isn’t as specific or direct a marker as a labs result showing elevated creatinine, which reflects the kidneys’ response to reduced perfusion.