Total Carbon Dioxide in Blood (Calculated from pH, pCO₂, and HCO₃⁻)

What Is Total CO₂ Used For?

Total CO₂ is primarily used in blood gas tests to evaluate how well your lungs are removing carbon dioxide and how your body is maintaining proper acid-base balance. It can help identify issues like respiratory acidosis (too much CO₂), respiratory alkalosis (too little CO₂), or metabolic disorders.

How Is This Test Performed?

A small sample of your blood is taken from an artery (often in your arm) and sent to a lab. The lab measures your blood’s pH, CO₂ pressure, and bicarbonate levels to calculate total CO₂. This test is usually done alongside other blood gas measurements, such as pH and pCO₂.

When Might You Need This Test?

Your doctor may order this test if you have symptoms like shortness of breath, fatigue, confusion, or rapid breathing. It’s also used in patients with chronic lung diseases (like COPD), kidney problems, or those who’ve had recent trauma or surgery.

What Are Common Causes of Abnormal Results?

Elevated total CO₂ levels may suggest respiratory acidosis (e.g., due to lung diseases or overuse of sedatives). Low levels could indicate respiratory alkalosis (e.g., from anxiety, high altitude, or overbreathing). Metabolic conditions or kidney issues may also affect bicarbonate levels indirectly.