What effect does dehydration have on laboratory test results?

Dehydration significantly impacts laboratory test results, and one of the primary effects is the false elevation of concentrations in blood tests. When a person is dehydrated, the volume of plasma in the bloodstream decreases, leading to hemoconcentration. This means that the solutes in the blood, such as electrolytes and metabolites, become more concentrated because there is less liquid to dilute them. As a result, tests such as serum sodium, potassium, and blood urea nitrogen (BUN) can show higher levels than they would in a well-hydrated state. This can lead to misleading interpretations and potentially inappropriate clinical decisions.

Additionally, while dehydration affects both blood and urine tests, it is particularly notable in blood tests where concentrations are more readily misrepresented. Other options presented suggest either no effect or limited effects, which do not fully encapsulate the impact that state of hydration can have on various laboratory results.