Taking blood sample. Needle and vacutainer being used to take a blood sample. The needle holder is being held by a medical worker's hand. The needle has been inserted into a vein (a process called venepuncture). A tourniquet (partly seen at top right) is used to make the veins more visible. The vacutainer is the tube inside the needle holder. It contains a partial vacuum that is drawing the blood (red) into the tube and out of the patient's arm. The sample of blood will be labelled and sent for testing.