How is the anion gap calculated?

The anion gap is a valuable calculation used primarily in the assessment of metabolic acidosis to identify the presence of unmeasured anions in the blood. This gap reflects the balance of electrolytes, specifically sodium (Na), chloride (Cl), and bicarbonate (HCO3−).

The correct method to calculate the anion gap is to subtract the sum of chloride and bicarbonate ions from the sodium concentration. This relationship effectively highlights the difference between the measured cations (like sodium) and the sum of the measured anions (like chloride and bicarbonate). Any discrepancy can indicate the presence of additional unmeasured anions, which can be vital for diagnosing various conditions, such as diabetic ketoacidosis, lactic acidosis, or renal failure.

In summary, the anion gap is calculated using the formula: Sodium - (Chloride + Bicarbonate), which allows for a clear assessment of the electrolyte imbalance in the context of metabolic processes.