Does low blood volume affect the results of blood tests?

Sarah94

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If I have low blood volume (which I don't know for sure, but strongly suspect), does that bias the results of blood tests? Both standard medical ones, and functional medicine ones like Genova NutrEval.
 

zzz

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If I have low blood volume (which I don't know for sure, but strongly suspect), does that bias the results of blood tests? Both standard medical ones, and functional medicine ones like Genova NutrEval.
It shouldn't. I've had my blood volume measured on a couple of occasions, and the plasma volume has been as much as 30% below the expected value. However, all my CBC values were completely normal. I can't say anything definitive about all blood tests, but due to the way the body regulates how much blood is circulated where, I would expect that other blood tests would be unaffected as well.
Good question. I have also wondered if drinking water beforehand, influences the results.
If you're severely dehydrated, then most blood test results will show higher levels than normal. Sufficient hydration in this case would cause the various test results to return to the normal range, assuming that no other problems exist. However, if you're not dehydrated, drinking a reasonable amount of water beforehand should not have any significant effect on the test results. This is why even for fasting blood tests, water is the one thing a person is permitted to consume before the tests.