text: Acid–base imbalance occurs when a significant insult causes the blood pH to shift out of the normal range (7.32 to 7.42). An abnormally low pH in the extracellular fluid is called an acidemia and an abnormally high pH is called an alkalemia.
  Acidemia and alkalemia unambiguously refer to the actual change in the pH of the extracellular fluid (ECF). Two other similar sounding terms are acidosis and alkalosis. They refer to the customary effect of a component, respiratory or metabolic. Acidosis would cause an acidemia on its own (i.e. if left "uncompensated" by an alkalosis). Similarly, an alkalosis would cause an alkalemia on its own. In medical terminology, the terms acidosis and alkalosis should always be qualified by an adjective to indicate the etiology of the disturbance: respiratory (indicating a change in the partial pressure of carbon dioxide), or metabolic (indicating a change in the Base Excess of the ECF). There are therefore four different acid-base problems: metabolic acidosis, respiratory acidosis, metabolic alkalosis, and respiratory alkalosis. One or a combination of these conditions may occur simultaneously. For instance, a metabolic acidosis (as in uncontrolled diabetes mellitus) is almost always partially compensated by a respiratory alkalosis (hyperventilation). Similarly, a respiratory acidosis can be completely or partially corrected by a metabolic alkalosis.