How is dehydration diagnosed?

• A. No single laboratory test confirms dehydration; diagnosis relies on multiple laboratory findings and clinical signs.
• B. A single elevated BUN confirms dehydration.
• C. Urine osmolality alone confirms dehydration.
• D. Blood glucose level confirms dehydration

Answer: (A)

Dehydration is diagnosed by putting together a clinical picture with supportive lab data; there isn’t one test that proves it. When someone is dehydrated, you look for signs of fluid loss and how the body is responding overall. Clinically, you’d assess history of reduced intake or ongoing fluid losses, thirst, dry mucous membranes, skin turgor (not always reliable in older adults), rapid heartbeat, low blood pressure or orthostatic changes, decreased urine output, weight loss, and any mental status changes.

Labs help but don’t confirm on their own. You might see concentrated urine (high urine osmolality and high specific gravity), a hemoconcentrated state with elevated hematocrit, and a higher BUN relative to creatinine (often with a BUN/creatinine ratio above typical values), all of which support a volume-depleted condition. Serum osmolality can be elevated, and sodium may be high if hypernatremia is present. These findings point toward dehydration when they fit the clinical scenario, but none single value alone proves dehydration, and other conditions can mimic or influence these results.

So the best choice reflects that no single laboratory test confirms dehydration; the diagnosis relies on multiple laboratory findings together with clinical signs.