Anion Gap
Cross References

The anion gap or electrolyte balance is calculated by the formula Na - (Cl +HCO3). In normal individuals most of the anion gap is due to protein. When an unmeasured anion such as ketones, lactate, formate, or oxalate is present an elevated anion gap results. While the values for the anion gap are method dependent, there is agreement that an anion gap > 16 is considered elevated. The reasons for a decreased anion gap are fewer and include low proteins, multiple myeloma (tend to be positively charged) and bromide ingestion (falsely counted as chloride). Patients may have a normal anion gap and still have acidosis. This is known as hyperchloremic acidosis where an elevated chloride compensates for the decreased bicarbonate.
See also:
Carbon Dioxide (CO2 Content), Plasma
Chloride, Plasma
Potassium, Plasma
Sodium, Plasma