A prolonged tourniquet time may lead to blood pooling at the venipuncture site, a condition called hemoconcentration. Hemoconcentration can cause falsely elevated results for glucose, potassium, and protein-based analytes such as cholesterol.

Ideally, the tourniquet should be in place no longer than one minute to prevent hemoconcentration. If the phlebotomist takes longer than one minute to assess and locate vein of choice for venipuncture, it is best practice to release the tourniquet, assemble supplies and reapply tourniquet immediately before needle insertion.