Hypoxia is most accurately defined as

• A. an increase in carbon dioxide in the blood.
• B. a decrease in arterial oxygen levels.
• C. inadequate oxygen to the tissues and cells.
• D. high oxygen levels in the tissues and cells.

Answer: (C)

Hypoxia means not enough oxygen is reaching the body's tissues and cells to meet their needs. It’s about tissue oxygen delivery, not just what’s in the blood. Even with normal arterial oxygen, problems like poor perfusion, anemia, or a failure of cells to use oxygen can create tissue hypoxia. That’s why the best description is inadequate oxygen to the tissues and cells.

In contrast, low arterial oxygen levels describe hypoxemia, which is a drop in oxygen content in the blood and can lead to hypoxia but isn’t the same thing by itself. A rise in carbon dioxide would indicate hypercapnia, not hypoxia. And high oxygen levels in the tissues would be hyperoxia, the opposite of hypoxia.