In medicine, venipuncture or venepuncture is the process of obtaining intravenous access for the purpose of venous blood sampling (also called phlebotomy) or intravenous therapy. In healthcare, this procedure is performed by medical laboratory scientists, medical practitioners, some EMTs, paramedics, phlebotomists, dialysis technicians, and other nursing staff. In veterinary medicine, the procedure is performed by veterinarians and veterinary technicians.

It is essential to follow a standard procedure for the collection of blood specimens to get accurate laboratory results. Any error in collecting the blood or filling the test tubes may lead to erroneous laboratory results.

Venipuncture is one of the most routinely performed invasive procedures and is carried out for any of five reasons:

1. to obtain blood for diagnostic purposes;
2. to monitor levels of blood components;
3. to administer therapeutic treatments including medications, nutrition, or chemotherapy;
4. to remove blood due to excess levels of iron or erythrocytes (red blood cells); or
5. to collect blood for later uses, mainly transfusion either in the donor or in another person.

Blood analysis is an important diagnostic tool available to clinicians within healthcare.

Blood is most commonly obtained from the superficial veins of the upper limb. The median cubital vein, which lies within the cubital fossa anterior to the elbow, is close to the surface of the skin without many large nerves positioned nearby. Other veins that can be used in the cubital fossa for venipuncture include the cephalic, basilic, and median antebrachial veins.

Minute quantities of blood may be taken by fingerstick sampling and collected from infants by means of a heelprick or from scalp veins with a winged infusion needle.

Phlebotomy (incision into a vein) is also the treatment of certain diseases such as hemochromatosis and primary and secondary polycythemia.