Anemia is characterized by a deficiency in what component of the blood?

Anemia is primarily characterized by a deficiency in either red blood cells or hemoglobin. Hemoglobin is the protein in red blood cells that carries oxygen throughout the body, and a reduction in either of these components results in a decreased capacity of the blood to transport oxygen, leading to symptoms such as fatigue and weakness.

Anemia can occur for various reasons, including blood loss, decreased red blood cell production, or increased destruction of red blood cells. This condition reflects a critical imbalance in the blood's composition, affecting overall health and well-being.

In contrast, the other options—white blood cells, platelets, and plasma volume—do not define anemia. White blood cells are primarily involved in the immune response, while platelets are essential for blood clotting. Plasma volume refers to the liquid component of blood that carries cells and proteins but is not directly related to the diagnosis of anemia. Therefore, a deficiency specifically in red blood cells or hemoglobin is what characterizes this condition.