Please have your iron levels tested before doing anything about otc iron supplement treatments. My ferritin levels were out of sight and extra iron can cause death! per my doctor. They never found a cause, Vitamin B is also a common cause, not a problem for me. Upper GI scope, colonoscopy and a GI pill camera showed no internal bleeding. It's known as idiopathic anemia. I've seen five hematologist and they are all stumped. More tests than I care to list. Idiopathic it is.
Prednisone treatment saw my hemoglobin so back to normal but like I said when I went off Prednisone it dropped. Definitely related.