Why take blood from a vein and not from an artery?

Sometimes we need to have blood drawn for health check-ups. The process of drawing blood for testing is called venipuncture. So how does the blood drawing process work, and why is blood drawn from a vein and not an artery?

Blood collection process

First, let's learn about veins and arteries.

Arteries are blood vessels that carry blood from the heart to the rest of the body, mostly oxygen-rich blood. There are two exceptions when arteries carry oxygen-poor blood. The first is the pulmonary artery, which carries blood from the heart to the lungs, and the second is the umbilical artery, which carries blood from the fetus to the placenta.

Veins are blood vessels that carry blood from the body back to the heart, so they are mostly oxygen-poor blood. However, the pulmonary and umbilical veins carry oxygen-rich blood. Veins also have valves to prevent backflow and have less muscle than arteries.

Venous blood can be used for many purposes such as intravenous therapy, blood testing, and diagnosis.

It is important to prepare all necessary supplies before starting the venipuncture procedure, including the blood collection needle, tourniquet, specimen collection tube, hand sanitizer, alcohol swabs, bandages, gauze, and blood transfusion equipment.

First, the patient straightens the arm, the tourniquet is tied 7-10cm above the needle site. The health care provider needs to identify a vein. In adults, the most common is the mid-cubital vein, a large blood vessel that makes blood collection easier and will also give good results if the blood is drawn correctly.

Why take blood from a vein and not from an artery?

Physically, veins are relatively easier to draw blood from because they are close to the skin surface. Meanwhile, arteries are located deeper below, so drawing blood is more difficult and painful for the patient.

Additionally, the pressure in a vein is lower than in an artery, so the chance of blood flowing back out before the wound heals is lower.