What is a haptoglobin (HP) test?
This test measures the amount of haptoglobin in the blood. Haptoglobin is a protein made by your liver. It attaches to a certain type of hemoglobin. Hemoglobin is a protein in your red blood cells that carries oxygen from your lungs to the rest of your body. Most hemoglobin is located inside red blood cells, but small amounts circulate in the bloodstream. Haptoglobin binds to hemoglobin in the bloodstream. Together, the two proteins are known as the haptoglobin-hemoglobin complex. This complex is quickly cleared from the bloodstream and removed from the body by your liver.
When red blood cells are damaged, they release more hemoglobin into the bloodstream. That means more of the haptoglobin-hemoglobin complex will be cleared from the body. The haptoglobin may leave the body faster than the liver can make it. This causes your haptoglobin blood levels to drop. If your haptoglobin levels are too low, it may be a sign of a disorder of the red blood cells, such as anemia.
Other names: hemoglobin-binding protein, HPT, Hp