What is the defining characteristic of metabolic acidosis?

Metabolic acidosis is characterized by a decrease in bicarbonate concentration in the blood. In this condition, the body either produces excess acid or loses bicarbonate, leading to a drop in the bicarbonate buffering capacity. This results in a lower pH, indicating acidosis. The fundamental disturbance in metabolic acidosis is the reduced level of bicarbonate, which plays a critical role in maintaining the acid-base balance in the body.

Increased carbon dioxide levels would typically indicate respiratory acidosis rather than metabolic acidosis and is not a defining characteristic of the metabolic process. The pH level is generally low in metabolic acidosis, so a normal pH would not align with this condition. Thus, the correct defining feature of metabolic acidosis is indeed the decreased concentration of bicarbonate in the bloodstream.