In an infant with an increased anion gap metabolic acidosis, the serum chloride would be which of the following?

• A. Decreased
• B. Increased
• C. Normal
• D. Elevated

Answer: (C)

In an increased anion gap metabolic acidosis, the loss of bicarbonate is outweighed by an accumulation of unmeasured anions (like lactate or ketoacids), which raises the anion gap. The chloride level does not typically rise in this situation because the acidosis is not driven by loss of bicarbonate with chloride retention; instead, the body’s balance shifts mainly with bicarbonate depletion and unmeasured anions. Therefore, the serum chloride tends to stay within the normal range. If chloride were elevated, that would point toward a hyperchloremic (normal anion gap) acidosis, not an increased anion gap one. Hence, normal chloride is the best answer.