Transferrin is the main iron transport protein in the blood that binds and delivers iron to cells throughout the body. This test measures transferrin levels to evaluate iron metabolism and nutritional status. Transferrin levels increase in iron deficiency as the body tries to transport more iron, and decrease in iron overload conditions or chronic inflammatory states. Transferrin is also an important marker of nutritional status, particularly protein nutrition, since it's produced by the liver. Low transferrin levels can indicate liver disease, malnutrition, or chronic inflammation, while high levels often suggest iron deficiency anemia. This test is commonly ordered when evaluating anemia, monitoring iron therapy, or when assessing overall nutritional status. Understanding transferrin levels helps distinguish between different types of anemia and guides appropriate treatment decisions.