Using Na 143 mmol/L, K 4.9 mmol/L, Cl 105 mmol/L, HCO3 25 mmol/L, the anion gap when potassium is included is approximately:

Using Na 143 mmol/L, K 4.9 mmol/L, Cl 105 mmol/L, HCO3 25 mmol/L, the anion gap when potassium is included is approximately:

• A. 13
• B. 18
• C. 23
• D. 28

Answer: (B)

When potassium is included, the anion gap is calculated as (Na + K) − (Cl + HCO3). This reflects unmeasured anions in the plasma, and including K raises the gap a bit compared with the formula that excludes K. Plugging in the numbers: Na + K = 143 + 4.9 = 147.9. Cl + HCO3 = 105 + 25 = 130. Subtracting gives 147.9 − 130 = 17.9, which rounds to about 18 mEq/L. Including potassium typically yields a normal range around 12–20 mEq/L, so 18 sits within normal limits. A higher gap would indicate excess unmeasured anions (like in certain metabolic acidoses), whereas a normal gap suggests a cause related to chloride or bicarbonate balance rather than unmeasured acids.

When potassium is included, the anion gap is calculated as (Na + K) − (Cl + HCO3). This reflects unmeasured anions in the plasma, and including K raises the gap a bit compared with the formula that excludes K.

Plugging in the numbers: Na + K = 143 + 4.9 = 147.9. Cl + HCO3 = 105 + 25 = 130. Subtracting gives 147.9 − 130 = 17.9, which rounds to about 18 mEq/L.

Including potassium typically yields a normal range around 12–20 mEq/L, so 18 sits within normal limits. A higher gap would indicate excess unmeasured anions (like in certain metabolic acidoses), whereas a normal gap suggests a cause related to chloride or bicarbonate balance rather than unmeasured acids.