Bicarbonate is a vital component of the pH buffering system of the body (maintaining acid-base homeostasis). 86%-90% of CO2 in the body is converted into carbonic acid (H2CO3), which can quickly turn into bicarbonate (HCO3-).
With carbonic acid as the central intermediate species, bicarbonate, in conjunction with water, hydrogen ions, and carbon dioxide forms this buffering system which is maintained at the volatile equilibrium required to provide prompt resistance to drastic pH changes in both the acidic and basic directions. This is especially important for protecting tissues of the central nervous system, where pH changes too far outside of the normal range in either direction could prove disastrous.
Bicarbonate levels are almost always done along with other electrolytes to tell your doctor whether your sodium, potassium, chloride, and bicarbonate levels are in balance. They may be measured as part of routine blood testing, or when your doctor suspects an imbalance. Bicarbonate may also be measured when your doctor is evaluating your acid-base balance, to screen for an imbalance, and to monitor a known problem during treatment.
When bicarbonate levels are higher than normal, it suggests that your body is having trouble maintaining its pH balance either by failing to remove carbon dioxide or perhaps because of an electrolyte imbalance, particularly a deficiency of potassium. Both of these imbalances may be due to a wide range of dysfunctions. Bicarbonate elevations may be seen with chronic lung-related problems, such as emphysema, and metabolic problems, such as severe diarrhoea or prolonged vomiting (which can cause metabolic alkalosis - as a consequence of loss of both acid and potassium). Low bicarbonate levels may be seen with respiratory alkalosis (which can be caused by hyperventilation), metabolic acidosis, shock, starvation, and during kidney failure.