Iron deficiency means there’s not enough iron in the body. This is a common cause of Anemia, although there are many other causes as well (see link to topic). We give iron supplements to treat anemia, and to prevent it during pregnancy. But if a person has anemia for another reason, iron won’t help at all (and can eventually cause liver damage).
In the U.S., it’s rare to find iron deficiency due to poor diet alone. Unless a person truly can’t access food, like elderly who are also poor and isolated, there’s enough iron in the various foods we manage to scrounge up that the body does OK. So whenever we see a patient with iron deficiency, we try to figure out why they’re losing iron, which is always due to some sort of bleeding.
There are only two places a person can lose too much blood (excluding injuries):
- Women with heavy or very long menstrual periods
- The gastrointestinal tract (stomach, small intestine, large intestine — see Diagram).
If a patient describes significant stomach pain, we might consider an ulcer as a source of the blood loss, & proceed accordingly with treatment and/or tests. Lots of bloody diarrhea obviously suggests the large intestine as a source. Black stools (bowel movements), not merely dark ones, could easily be clotted blood from the stomach, small intestine, or the beginning of the large intestine (the cecum). Iron pills can turn stools black, as can bismuth preparations like Pepto-Bismol®.
Young women (<40) with heavy periods don’t need more tests. We simply give her iron supplements, & do testing if the anemia doesn’t improve. Everyone else should have endoscopy and colonoscopy to look inside the stomach and large intestine. Even if no cause of bleeding can be found, the main thing is to make sure there’s no stomach or bowel cancer.
If those exams are negative, we might try to look inside the small intestine (the patient swallows a tiny video camera on a string). We almost never find anything. Another important test to do is an anti-tissue transglutaminase IgA antibody, a blood test for Celiac Disease.
If nothing shows up, and the patient remains iron deficient, we’d likely let a Gastroenterologist or maybe Hematologist determine what more studies need to be done.