Most tests do not require special preparation. As with any blood test, the health care provider may limit certain foods or medications shortly before the test to assure an accurate sample. 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 . 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 body, tests on the blood or its components may give valuable clues in the diagnosis of a multitude of medical conditions. Normal results vary with the specific test. The cost varies with the specific test. Veins and arteries vary in size from one patient to another and from one side of the body to the other.