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Metabolic acidosis
Other Resources UpToDate PubMed

Metabolic acidosis

Contributors: Scott Echternacht MD, Christine Osborne MD, Catherine Moore MD, Michael W. Winter MD
Other Resources UpToDate PubMed


Metabolic acidosis is an acid-base imbalance in the body due to increased hydrogen ion concentration and a reduction in bicarbonate concentration. Patients will have an acidotic, or low, pH (< 7.35), although in cases of mixed acid-base disturbances, patients with an underlying metabolic acidosis may have low, normal, or high pH values. The development of a metabolic acidosis occurs in 1 of the following 4 ways:
  • Increased acid generation – Lactic acidosis from decreased perfusion or sepsis, ketoacidosis due to poorly controlled diabetes, excess alcohol ingestion or starvation, medication or ingestion adverse effect (eg, methanol, ethylene glycol, diethylene glycol, propylene glycol, aspirin, chronic use of acetaminophen, and toluene).
  • Increased bicarbonate loss – Profuse diarrhea, proximal renal tubular acidosis (RTA), or loss of ketoacid anions in the urine during ketoacidosis.
  • Diminished renal acid excretion – Reduced acid secretion in the setting of reduced glomerular filtration rate. This occurs in chronic kidney disease, distal RTA, and type 4 RTA due to tubular dysfunction.
  • Dilution acidosis – A decrease in serum bicarbonate concentration due to extracellular fluid volume expansion with alkali-free isotonic intravenous (IV) fluid. This only occurs with large-volume infusion of alkali-free isotonic fluid (ie, 5% dextrose solution [D5W]).
Metabolic acidosis can be classified as either normal anion gap or increased anion gap. To calculate the anion gap: [Na] - ([Cl] + [HCO3]) with normal values ≤ 12 mEq/L. To evaluate possible causes of metabolic acidosis with a normal anion gap or hyperchloremic metabolic acidosis, remember the acronym HARDASS:
  • Hyperalimentation
  • Addison disease (hypocortisolism)
  • Renal tubular acidosis
  • Diarrhea
  • Acetazolamide
  • Spironolactone
  • Saline infusion
To evaluate possible causes of metabolic acidosis with an increased anion gap, remember the acronym MUDPILES:


E87.21 – Acute metabolic acidosis

59455009 – Metabolic acidosis

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Last Reviewed:01/30/2019
Last Updated:03/03/2024
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Metabolic acidosis
A medical illustration showing key findings of Metabolic acidosis : Diarrhea, Headache, Ketoacidosis, Dyspnea
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