Capillary blood tests are performed to test the blood for nutrients, gases, oxygen levels and waste product levels in the body. It is a simple test that can help doctors determine certain blood levels without drawing blood from a vein, notes MedlinePlus.
A capillary blood sample is taken by pricking the skin. Often, these blood tests are performed on the fingertips or heels. The small amount of blood collected can be tested for various blood levels. Capillary blood tests are easy to perform and are very quick. They have minimal risks and can even be performed at home by the patient in certain circumstances.