Generally a nurse or a phlebotomy technician performs venesection, also known as phlebotomy. A vein in upper forearm (antecubetal fossa) is used for blood collection mostly. Blood gas measurements use arterial blood. Capillary bed is used for smaller quantity of blood and a capillary puncture or skin puncture is the method used. Point of care tests use the minimum quantity of blood and are performed by capillary puncture.

Venous blood can be collected in many ways. Venipuncture methods can vary depending on the test requirements, age, and physical condition of the patients. The sites to use are those in forearm, wrist, or ankle but the common is forearm veins. This is because forearm veins are generally more fuller and larger than other veins. Three main veins in the forearm are cephalic, median cubital, and median basilic.

An evacuated tube and needle collection system or a sterile syringe and needle can be used for collection of blood from a vein. BD Vacutainer system tubes are widely used where BD represents the company Becton, Dickinson and company, which first marketed these tubes. Evacuated tubes can be combined to use in an infusion or butterfly set.

A double ended hypodermic needle is used to puncture the vein in the evacuated tube method, where the shorter end of needle is covered by the holder for phlebotomist safety. One end of the needle is inserted into the vein and the other end is partially attached to a rubber stopper of a special vacuum tube. The rubber cap of the holder is pierced by the second needle when the vacutainer test tube is pushed down into the holder, and this creates a pressure difference in the blood volume and the blood is forced through the needle into the tube by the vacuum present in the tube. Next sample is collected in the same way after removing the tube and inserting another tube. The presence of suction in the tube makes it important to remove the tube before withdrawing the needle from the vein. Evacuated tubes are used for blood specimen collection as per standards set by The Clinical and Laboratory Standards Institute (formerly NCCLS).

In patients with difficult veins the use of a syringe and needle system is made for collection of blood. Vacuum of BD vacutainer tubes may cause collapsing of smaller veins in some patients, and in this case use of syringe and needle is preferred. In case of collection for babies, and small children with small veins, for obese patients with hard to find veins, for patients receiving intravenous therapy with scarred veins, and for veins other than those in antecubital fossa (wrist, back of hand, ankle, foot, or scalp), an infusion set called butterfly is often used.

The duties as a phlebotomist of technicians vary depending on the workplace. In a hospital, the phlebotomists primary duty is to assist doctors. The technician also coordinates with nurses. One of the duties as a phlebotomist of a hospital technician is to take blood or tissue samples from patients.

Proper patient identification is an important process before sample collection for a phlebotomist. Correct puncture or incision of patients skin to take specimens is the responsibility of a phlebotomist. Enough volume of blood or tissue should be taken for the specific test and this is the duty of the phlebotomist. Phlebotomists role also is to correctly label the sample and transport the labeled samples to the testing lab on time.

To achieve these competencies, training from a certified program, or on job training, or cross training from other healthcare profession can be completed by the phlebotomists. Professional association certification leads to fine tuned skills for already employed technicians / phlebotomists and learning basic skills for new graduates.