Which type of hypoxia is caused by reduced oxygen-carrying capacity due to low hemoglobin?

• A. Hypoxic hypoxia
• B. Anemic hypoxia
• C. Histotoxic hypoxia
• D. Stagnant hypoxia

Answer: (B)

Oxygen delivery depends on the blood’s capacity to carry oxygen, which is set by hemoglobin binding the O2. When hemoglobin is reduced or dysfunctional, the arterial oxygen content falls even if the lung’s oxygen tension is normal, so tissues receive less O2. This is anemic hypoxia: the oxygen shortfall comes from reduced carrying capacity, not from a lack of oxygen in the air or an inability of cells to use it. Unlike hypoxic hypoxia, where low arterial PO2 limits oxygen reaching the blood, histotoxic hypoxia where cells can’t utilize O2, or stagnant hypoxia where blood flow is impaired, anemic hypoxia centers on having too little hemoglobin to transport the available oxygen.