The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding . 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 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.