How can a tourniquet affect a blood test?

A tourniquet can affect a blood test by temporarily restricting blood flow, which may lead to hemoconcentration. This can cause an increase in the concentration of certain substances in the blood, such as proteins and electrolytes, potentially skewing test results. Additionally, prolonged application of a tourniquet can cause the release of potassium from cells, falsely elevating potassium levels in the sample. It's important for healthcare providers to apply and remove the tourniquet properly to minimize these effects.