An AFP tumor marker test is a blood test that measures the level of AFP (alpha-fetoprotein) in a sample of your blood. AFP is a protein that the liver makes when its cells are growing and dividing to make new cells. AFP levels are normally high in a fetus, but after birth, they drop very low. Healthy children and adults who aren’t pregnant have very little AFP in their blood.

Source: MedlinePlus, U.S. National Library of Medicine