Bicarbonate is a group of atoms in liquid solution forming the chemical formula HCO3-. Within living organisms, it plays a vital role in balancing the acidity of bodily fluids, most importantly blood. In it's pharmaceutical forms (such as sodium bicarbonate), it is used to treat acidosis, but in a person with a normal metabolism, almost 75% of the carbon dioxide in the body is used in the process to create bicarbonate naturally. Testing for bicarbonate concentrations in blood is an important diagnostic indicator of several conditions.