What blood test values would someone use to check for dehydration?

Nothing specific: Dehydration is usually a clinical diagnosis based on the pattern of urine production. For infants and kids, no pee in 6-8 hours usually means they are dry.Older kids and adults are given a bit more time, but electrolyte studies, the BUN, the concentration of the hematocrit, can all can be found to support the clinical diagnosis.By themselves, lab tests can be normal at most states of hydration.