What is the formula for calculating the Anion Gap?

The Anion Gap is a valuable clinical tool used to help determine the cause of metabolic acidosis. It reflects the difference between the primary measured cations and anions in serum. The correct formula for calculating the Anion Gap is based on the concentrations of sodium (Na), chloride (Cl), and bicarbonate (HCO3).

The properly structured formula, Na - (Cl + HCO3), captures the essential elements. Sodium is the primary cation, and the sum of chloride and bicarbonate represents the primary measured anions. By subtracting the sum of chloride and bicarbonate from sodium, you can determine whether there are unmeasured anions present, which is key in diagnosing different types of metabolic disturbances.

In clinical practice, an increased Anion Gap often suggests the accumulation of unmeasured anions, which can occur in conditions such as diabetic ketoacidosis, renal failure, or lactic acidosis. Understanding this formula is vital for healthcare professionals when diagnosing and managing acid-base disorders.