People with Crohn's disease often have anemia due to vitamin B 12 , folate , iron deficiency , or due to anemia of chronic disease .   The most common is iron deficiency anemia  from chronic blood loss , reduced dietary intake, and persistent inflammation leading to increased hepcidin levels, restricting iron absorption in the duodenum.  As Crohn's disease most commonly affects the terminal ileum where the vitamin B12/ intrinsic factor complex is absorbed, B12 deficiency may be seen.  This is particularly common after surgery to remove the ileum.  Involvement of the duodenum and jejunum can impair the absorption of many other nutrients including folate. If Crohn's disease affects the stomach, production of intrinsic factor can be reduced.