Multiple. Iron deficiency (microcytic hypochromic) is one of the main causes but there are others: vitamin b12/folate deficiency (macrocytic), chronic disease like infection or cancer (normocytic normochromic), genetic conditions (thalassemia), certain medications, toxins, etc. Consulting with your doctor or a hematologist for proper testing and diagnosis is a must before starting any treatment.
Many causes. Low level of hemoglobin, hematocrit, number of red blood cells is called anemia, but many things can cause their levels to be decreased such as: bleeding, destruction of the red cells, low iron, low productions of red cells by the bone marrow, genetic defects, faulty hemoglobin molecules (sickle anemia), malignancy, renal disease. Types: microcytic, macrocytic, normocytic, hemolityc.