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.
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. The disadvantages are the limited amount of blood that can be obtained and the inaccuracy of capillary blood for some testing. Capillary sample Please read this Important notice .