What is the normal range for the anion gap?

What is the normal range for the anion gap?

• A. 4-10 mEq/L
• B. 2-6 mEq/L
• C. 15-20 mEq/L
• D. 8-14 mEq/L

Answer: (D)

Anion gap reflects unmeasured anions and is calculated as Na minus (Cl plus HCO3). In many laboratories and exams, a normal value is about 8–12 mEq/L, with a range often cited up to about 14 mEq/L to accommodate variation between labs. Among the options given, 8–14 mEq/L sits closest to the commonly accepted normal range. Why this range matters: if the gap is elevated, there are extra unmeasured acids in the blood (like lactate, ketones, or toxins) contributing to metabolic acidosis. If the gap stays normal but a metabolic acidosis is present, it’s typically a hyperchloremic type where chloride rises to balance bicarbonate. Albumin levels also affect the gap—low albumin lowers the gap, high albumin can raise it. The other ranges are not consistent with standard normal values: a range around 4–10 would be relatively low, 2–6 too low, and 15–20 would be considered elevated, suggesting abnormal metabolism.

Anion gap reflects unmeasured anions and is calculated as Na minus (Cl plus HCO3). In many laboratories and exams, a normal value is about 8–12 mEq/L, with a range often cited up to about 14 mEq/L to accommodate variation between labs. Among the options given, 8–14 mEq/L sits closest to the commonly accepted normal range.

Why this range matters: if the gap is elevated, there are extra unmeasured acids in the blood (like lactate, ketones, or toxins) contributing to metabolic acidosis. If the gap stays normal but a metabolic acidosis is present, it’s typically a hyperchloremic type where chloride rises to balance bicarbonate. Albumin levels also affect the gap—low albumin lowers the gap, high albumin can raise it.

The other ranges are not consistent with standard normal values: a range around 4–10 would be relatively low, 2–6 too low, and 15–20 would be considered elevated, suggesting abnormal metabolism.