What's causing my iron deficiency?

craigh47, I'd guess GI bleeding because of having Crohn's. But you may not be producing enough rbc or may have a condition that is destroying. I'd want a colonoscopy. Do you have a gastroenterologist.

@gently I do have a GI. I also see an Oncologist and Hematologist. I get scoped at least once a year because of my Crohn's, they haven't seen any internal bleeding.

craigh47, radiation can play havoc with blood cell production. Is the oncologist a clue, but they would know that.
Are other blood counts normal. Have you been tested for intrinsic factor deficiency. Do your doctors know, or are they trying to figure it out.

I have not been tested for that and the various doctors are trying to figure things out with little to no luck.

I'm a patient. What you have is likely malabsorption. I have had the same problem with iron. Crohn's affects most people in this way I suspect. Malabsorption leads to malnutrition. When our GI system is compromised, this can happen. Our small intestines simply can't quite get the iron we need. Continue working with your doctors and doing what you can to improve absorption and reduce Crohn's symptoms.