What is the formula for calculating the anion gap?

The formula for calculating the anion gap is recognized as a critical part of evaluating acid-base balance in patients. The correct formula is derived from the major electrolytes present in the blood, specifically sodium (Na), potassium (K), bicarbonate (HCO3), and chloride (Cl). The anion gap helps to identify the presence of unmeasured anions when metabolic acidosis is suspected.

In this formula, the anion gap is calculated using sodium and potassium as the primary cations, while bicarbonate and chloride are used as the primary anions. This is because, in metabolic acidosis, the presence of additional unmeasured anions is what influences the gap.

By subtracting the sum of bicarbonate and chloride from the sum of sodium and potassium, healthcare providers can discern abnormalities in acid-base balance and aid in diagnosing conditions like diabetic ketoacidosis, lactic acidosis, or renal failure.

While other options present various combinations of these electrolytes, they do not represent the standard calculation used in clinical practice, which is focused on sodium and potassium as cations and bicarbonate and chloride as anions for the purpose of evaluating the anion gap.