What is the proper pressure of a tourniquet in phlebotomy?

In phlebotomy, the appropriate tourniquet pressure should not exceed 80 mm Hg. Applying moderate pressure prevents the superficial pooling of blood without impeding the arterial supply to the arm. After drawing the blood sample, the tourniquet should be completely removed before removing the needle from the vein to avoid squeezing out excess blood and potential clotting.