Hat can cause a lock of iron in a man without any bleeding found.

Dietary deficiency: Dietary deficiency of iron can cause low iron, however, before coming to that conclusion, i would rule out all causes of bleeding including hidden ones, such as intestinal cancer.

Celiac sprue, diet: Lack of iron is due to lack of intake, increased loss (gross or occult bleeding- usually gastrointestinal (gi), less often urinary), or poor absorption-usually celiac sprue. Less often other GI causes. See your doc. Screening for celiac is simple blood testing. Diet diary. May need GI workup to rule out other problems, such as fragile blood vessels, tumors, parasites, or cancers.