The median cubital vein connects the basilic vein and the cephalic vein in the upper arm. Together these three veins typically form an H-shaped pattern, with the basilic vein in the middle of the arm, the cephalic vein on the outside of the arm and the median cubital vein forming the bar between the cephalic and basilic veins. The median cubital vein is located in the cubital fossa, which is the area on the upper arm that becomes creased when the elbow is bent; some people refer to this as the "elbow pit."

Veins are blood vessels that carry the blood toward the heart. The median cubital vein is part of a network of veins that take deoxygenated blood from the hand and forearm to the heart and lungs. After the blood is oxygenated in the lungs, it can be circulated to the rest of the body through arteries.

Phlebotomists and nurses are trained to look for the median cubital vein when they need to perform draw blood. The cephalic vein can be difficult to use for such venipuncture because it has a tendency to roll away when the needle makes contact with it. Unlike the basilic vein, the median cubital vein is fairly short, and when the elbow is extended, the skin and muscles become taught, which helps secure the median cubital vein in place. This prevents the vein from rolling out from under the needle.

The median cubital vein is superficial, which means that it is near the surface. This makes the vein easy to locate by pressing lightly along the skin on the inside of the elbow. Although there is some variation from one person to another, the location is fairly consistent, making it easy to locate. If the medial cubital vein has been damaged by repeated blood draws or if there is severe bruising in the area, then another vein is often used.