Iron deficiency, either through lack of iron in the diet or absorption issues, causes low ferritin, B-12 and iron levels, according to Mayo Clinic. Other vitamins, such as B-12, C, folate and zinc, assist in more efficient iron absorption, according to the Iron Disorders Institute.
Ferritin is a protein found in blood cells that contains iron. Low ferritin, or decreased absorption of iron, often occurs in those with minimal or no heme iron their diet. Meat and fish contain heme iron. Vegetables and supplements, referred to as nonheme iron, are not absorbed as efficiently as heme iron, explain the Iron Disorders Institute. After test results show low ferritin levels, a physician works to determine the cause and find ways to improve ferritin levels, often through supplementation.