What is the bicarbonate value (HCO3-) in the ABG sample?

• A. 25
• B. 18
• C. 30
• D. 20

Answer: (A)

Bicarbonate (HCO3-) shows the metabolic portion of the acid-base status in an ABG. Its normal range is about 22–26 mEq/L, and it serves as the major bicarbonate buffer in blood. When the pH is normal and the PCO2 is near 40 mmHg, the HCO3- value typically sits around 24 mEq/L.

A value of 25 mEq/L falls squarely within that normal range, suggesting no metabolic acidosis or metabolic alkalosis in this sample. The other numbers would indicate a metabolic disturbance: a lower HCO3- (like 18 or 20) points to metabolic acidosis, while a higher HCO3- (like 30) points to metabolic alkalosis.