An elevated anion gap metabolic acidosis is typically due to accumulation of what?

• A. Hyperchloremia alone
• B. Increased bicarbonate
• C. Unmeasured cations such as potassium
• D. Unmeasured anions such as lactate and ketoacids

Answer: (D)

An elevated anion gap in metabolic acidosis means there are extra unmeasured anions accumulating in the blood. The standard way we think about this is Na+ minus (Cl− plus HCO3−). When organic acids like lactate or ketoacids build up, they add negative charges that aren’t accounted for in the measured anions, widening the gap and producing the classic high anion gap picture.

Hyperchloremia tends to cause a normal (or near-normal) anion gap acidosis because the added chloride is a measured anion, which balances the loss of bicarbonate without widening the gap.

Increased bicarbonate would reduce acidity, not create acidosis.

Unmeasured cations such as potassium don’t drive the anion gap; the gap reflects unmeasured anions, not cations.

So the accumulation of unmeasured anions like lactate and ketoacids best explains an elevated anion gap metabolic acidosis.