What does a blood pH lower than 7.35 primarily indicate?

A blood pH lower than 7.35 indicates acidosis. The normal range for blood pH is typically between 7.35 and 7.45. When the pH drops below 7.35, it signifies an excess of hydrogen ions in the blood, leading to a state of acidosis. This condition can arise from various causes, including respiratory issues where the body fails to expel enough carbon dioxide (a contributor to acidic blood pH), metabolic factors such as kidney dysfunction, or increased production of acids due to conditions like diabetic ketoacidosis.

In contrast, a blood pH above 7.45 would indicate alkalosis, a state characterized by a deficiency of hydrogen ions. Homeostasis refers to the body's ability to maintain stable internal conditions, and while maintaining pH is a part of homeostasis, a pH lower than the normal range is indicative of a specific deviation from this state rather than homeostatic balance. Respiratory failure may lead to acidosis, but it is not directly defined by the pH measurement alone; rather, it is a potential cause of the condition. Therefore, the primary interpretation of a blood pH lower than 7.35 is that it reflects acidosis.