In medicine, metabolic acidosis is an acid-base imbalance in which the blood pH is low (less than 7.35) due to increased production of H⁺ by the body or the inability of the body to form bicarbonate (HCO₃^–) in the kidney. Its causes are diverse, and its consequences can be serious, including diarrhea, coma and death. Together with respiratory acidosis, it is one of the two general types of acidosis, the other being respiratory acidosis.

A pH under 7.1 is an emergency, due to the risk of cardiac arrhythmias, and may warrant treatment with intravenous bicarbonate. Bicarbonate is given at 50-100 mmol at a time under scrupulous monitoring of the arterial blood gas readings. This intervention however, is not effective in case of lactic acidosis. If the acidosis is particularly severe and/or there may be intoxication, consultation with the nephrology team is considered useful, as dialysis may clear both the intoxication and the acidosis.