Metabolic acidosis occurs when acid generation exceeds _______.

• A. Buffering capacity
• B. Oxygen delivery
• C. Bicarbonate production
• D. Carbon dioxide elimination

Answer: (A)

Metabolic acidosis happens when the amount of acid in the body overwhelms the buffering systems. The main extracellular buffer is bicarbonate, which neutralizes hydrogen ions to form carbonic acid that’s ultimately expelled as CO2. When acid generation exceeds the body’s buffering capacity, buffers are used up faster than they can be replenished, bicarbonate levels drop, hydrogen ions accumulate, and the pH falls. That’s why buffering capacity is the best fit.

Oxygen delivery doesn’t define this condition, and bicarbonate production would help buffer acids rather than cause acidosis. Carbon dioxide elimination is a respiratory adjustment that the body uses to compensate for metabolic acidosis, not the primary cause.