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.
Results vary depending on the test performed.
The estimated cost is calculated per test, not for taking the sample. See the specific test. The results of capillary testing may be very accurate for some tests, but for other tests they may be less accurate. Blood is routinely drawn from newborn infants for testing. Routine testing includes phenylketonuria and blood type.