How long should a tourniquet be left on pt arm during venipuncture procedure?

A tourniquet should not be left on a patient's arm during a venipuncture procedure. It should only be used to make the vein more prominent for a short period before the needle is inserted. Leaving the tourniquet on for an extended period can cause discomfort, bruising, and potential damage to the vein. Always release the tourniquet as soon as the blood starts to flow into the collection tube or syringe.