Doctors can tell a lot from looking at a patient's blood, and in order to do that, they depend on phlebotomy — the medical specialty of collecting blood using a needle.
In some cases, phlebotomy can help to diagnose a patient with a particular illness. The person who inserts the needle, draws the blood, labels the test tubes, and puts a bandage on the patient's arm is called a phlebotomist. The original definition of phlebotomy was simply "bloodletting," from the Greek roots phleps, "vein," and tomia, "cutting off." Historically, early phlebotomy involved using leeches to suck "toxins" from patients' blood.