Phlebotomy simply means to cut into a vein. The term comes from phlebos, Greek for "vein" and tome, "to cut." This invasive procedure (procedure that invades the body through cutting or puncture) is performed by professionals known as phlebotomists. Phlebotomists must demonstrate mastery of the principles and techniques established by the Clinical and Laboratory Standards Institute (CLSI ), formerly known as the National Committee for Clinical Laboratory Standards (NCCLS) .

The primary role of a phlebotomist is to obtain blood specimens for diagnostic testing, either by venipuncture (puncturing the vein) or dermal puncture (puncturing the skin). Another role of the phlebotomist is to remove blood from donors for blood transfusions, or from patients with a condition called polycythemia (overproduction of red blood cells), in which blood must be removed to decrease the viscosity (thickness) of the blood. Phlebotomists are also responsible for collecting and properly packaging urine specimens, accepting incoming specimens (blood and body fluids, etc.), and routing specimens to the proper departments to be tested and analyzed.