Harr Clinical Chemistry Practice Test 2026 – Complete Exam Prep

In arterial blood, the normal ratio of bicarbonate (HCO3-) to dissolved carbon dioxide (dCO2) is approximately 20:1. This ratio is critical in maintaining the acid-base balance within the body, as bicarbonate acts as a buffer to neutralize excess hydrogen ions and helps regulate the pH of blood.

The bicarbonate ion plays a central role in the bicarbonate buffer system, which is one of the primary buffering systems in the extracellular fluid. Through the interaction of bicarbonate and carbon dioxide, this system crucially maintains homeostasis. When the body is functioning optimally, the bicarbonate concentration is about 20 times higher than that of dissolved CO2. This allows for efficient removal of carbon dioxide, produced as a metabolic waste product, thus preventing acidosis.

This 20:1 ratio is commonly referenced in clinical settings when assessing a patient's acid-base status. Deviations from this normal ratio can indicate various metabolic or respiratory disorders, highlighting its importance in diagnostic evaluations.