Capillary sample

Alternative names:

blood sample - capillary; fingerstick; heelstick

How the test is performed:

Some blood tests may be performed on blood obtained by pricking the skin of the finger, heel, or other areas (capillary blood) and collecting a drop (or a few drops) of blood on a test strip or into a small container.

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test:

The preparation varies with the test performed.

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

Blood is used by the body for transportation of oxygen, food, waste products, and other materials within the body. It is also used for regulation of body temperature, regulation of fluids, and acid-base equilibrium. Blood is made up of a fluid portion (plasma) and a cellular portion. Plasma contains various substances dissolved in the fluid. The cellular portion consists primarily of red blood cells, but also includes white blood cells and platelets. Because blood is used for multiple functions within the blood, tests on the blood or its components may give valuable clues in the diagnosis of a multitude of medical conditions.

Capillary blood sampling offers the advantages of easy obtainment (no need to "hunt" for a vein), the ability to rotate sites, and the ability to be performed at home and with minimal training. The disadvantages are the limited amount of blood that can be obtained and the inaccuracy of capillary blood for some testing.