Metabolic acidosis is characterized by HCO3- levels below which value?

• A. 26 mEq/L
• B. 22 mEq/L
• C. 28 mEq/L
• D. 18 mEq/L

Answer: (B)

Metabolic acidosis shows up when the bicarbonate buffering system is diminished, usually from producing too much acid or losing too much bicarbonate. Bicarbonate buffers hydrogen ions, so when its level falls, the blood becomes more acidic. The body attempts to compensate by increasing ventilation to blow off CO2, which helps push the pH back toward normal.

Clinically, metabolic acidosis is defined by bicarbonate falling below the normal lower limit. In exam contexts, the threshold is the point where bicarbonate leaves the normal range and indicates a metabolic disturbance, rather than a purely respiratory one or a normal state. Values at or above the lower limit do not indicate metabolic acidosis, while lower values point to this condition.