Anion Gap Formula and Calculator

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Anion Gap Calculator

Interpretation of the results of anion gap (albumin or non-albumin corrected)

Anion GapCauses
High Anion Gap due to excess acid (AG >16)Lactic acidosis
Ketoacidosis - starvation ketosis, alcohol or diabetic ketoacidosis
Uremia
Methanol or Ethanol
Rhabdomyolysis
Salicylate toxicity
Isoniazid/Paraldehyde/Iron toxicity
Normal Anion Gap due to renal or extra-renal (gastrointestinal) losses of bicarbonate (AG 8-16)GI losses (enterocutaneous fistula, diarrhea, colostomy, ileostomy)
Isotonic saline infusion
Renal tubular acidosis (type I or IV)
Uteropelvic shunt
Cholestyramine/Acetazolamide
Addison's disease
Low anion gap (<8)Albumin (decreased unmeasured anions)
Calcium, magnesium, lithium (increased unmeasured cations)
Laboratory error

Interpretation of the results of delta ratio 

Delta ratioInterpretation
0 to 0.4Hyperchloremic normal/non-anion gap acidosis
0.4 to 1.0High anion gap acidosis and normal anion gap acidosis
1 to 2High anion gap acidosis
>2High anion gap acidosis with co-existing metabolic alkalosis or fully compensated respiratory acidosis

Interpretation of the results of delta gap (albumin or non-albumin corrected)

Delta GapInterpretation
<18 Concomitant non-anion gap metabolic acidosis
18-30No additional metabolic perturbations
>30Concomitant metabolic alkalosis

References

Oh MS, Carroll HJ. The anion gap. N Engl J Med. 1977 Oct 13;297(15):814-7. doi: 10.1056/NEJM197710132971507. PMID: 895822.

About the Author MyEndoConsult

The MyEndoconsult Team. A group of physicians dedicated to endocrinology and internal medicine education.

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