Question 1

What does a high anion gap indicate?

Accepted Answer

A high anion gap (>12 mEq/L) suggests the presence of unmeasured anions, typically from metabolic acidosis. Common causes include lactic acidosis, diabetic ketoacidosis (DKA), renal failure, and toxic ingestions (methanol, ethylene glycol, salicylates).

Question 2

What is a normal anion gap?

Accepted Answer

The normal anion gap is typically 8–12 mEq/L when calculated as Na − (Cl + HCO₃). If potassium is included, the normal range shifts to 10–14 mEq/L. Labs using ion-selective electrodes may have slightly different reference ranges.

Question 3

What is a non-anion-gap metabolic acidosis?

Accepted Answer

A non-anion-gap (or hyperchloremic) metabolic acidosis has a normal anion gap with low bicarbonate. Causes include diarrhea, renal tubular acidosis (RTA), and use of carbonic anhydrase inhibitors.

Question 4

Should I correct the anion gap for albumin?

Accepted Answer

Yes. Albumin is the major unmeasured anion. In hypoalbuminemia, the anion gap may appear falsely normal. The corrected anion gap adds approximately 2.5 mEq/L for each 1 g/dL decrease in albumin below 4.0 g/dL.

Anion Gap (mEq/L)	Interpretation
< 8	Low
8 – 12	Normal
> 12	Elevated

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