Which ABG result best indicates metabolic alkalosis?

• A. High pH and high HCO3
• B. Low pH and low HCO3
• C. Normal pH with high HCO3
• D. High pH with low HCO3

Answer: (A)

Metabolic alkalosis is defined by a primary increase in bicarbonate (HCO3−) that pushes the blood toward alkalinity. The clearest ABG pattern for this is an elevated pH (alkalemia) together with an elevated HCO3−. The rise in bicarbonate is what genuinely reflects the metabolic origin, and the body may compensate by hypoventilating to raise CO2, but that does not change the fact that the key indicator is high pH with high HCO3−.

If you see a high pH with low HCO3−, that points more toward a respiratory cause (low CO2) or a mixed disorder, not metabolic alkalosis. A normal pH with high HCO3− could occur if there is complete respiratory compensation, but the most straightforward and definitive clue for metabolic alkalosis remains alkalemia with elevated bicarbonate.