As a healthcare professional with expertise in diagnostics, I can tell you that there isn't a single blood test that directly shows dehydration. However, several blood tests can indirectly indicate dehydration by measuring the concentration of certain substances in the blood. Here's how:


1. Hematocrit (HCT): This measures the proportion of red blood cells in the blood. When you're dehydrated, your blood can become more concentrated, which can raise the hematocrit level.


2. Blood Urea Nitrogen (BUN): This test measures the amount of urea nitrogen in the blood, which can increase when you're dehydrated because the kidneys receive less blood, leading to less efficient filtering.


3. Sodium (Na+) Levels: High levels of sodium in the blood can be a sign of dehydration, as the body retains sodium when trying to maintain fluid balance.


4. Osmolarity: This measures the concentration of particles in the blood. An increase in osmolarity can indicate dehydration.


5. Creatinine: This is a waste product that is usually excreted in urine. If the creatinine level is high, it could suggest that the kidneys are not receiving enough water to filter waste effectively, which can be a sign of dehydration.


6. Specific Gravity of Urine: While not a blood test, this is a common test to assess hydration status. A specific gravity greater than 1.020 can indicate dehydration.

It's important to note that these tests are not definitive for dehydration and should be interpreted in the context of the patient's symptoms and medical history. A healthcare provider would typically use a combination of physical examination, patient history, and these lab results to determine if a patient is dehydrated.

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To help confirm the diagnosis and pinpoint the degree of dehydration, you may have other tests, such as: Blood tests. Blood samples may be used to check for a number of factors, such as the levels of your electrolytes �� especially sodium and potassium �� and how well your kidneys are working. Urinalysis.read more >>