Normal anion gap acidosis is an acidosis that is not accompanied by an abnormally increased anion gap.

The most common cause of normal anion gap acidosis is diarrhea with a renal tubular acidosis being a distant second.

The differential diagnosis of normal anion gap acidosis is relatively short (when compared to the differential diagnosis of acidosis): As opposed to high anion gap acidosis (which involves increased organic acid production), normal anion gap acidosis involves either increased production/administration of chloride (hyperchloremic acidosis) or increased excretion of bicarbonate.