Prety much with crohns almost everything will be out of order,,, because having Crohns if to have our intestine COATED with a mucus that prevents absorbsion, malnuriment, weak, sickly looking, bones hurt, teeth issue nomatter how much you brush[thats make you all see dentist every year] ,skin,eyes ect.... It does sound scarey ,but, we all get use to it in our oun way, and learn to live........ B12 is easy to get , you will get your energy back.......Anyone have low B12 prior to diagnosis?
My first surgery in the NAVY  my doctors told me how the intestines work as in when aborbsion starts , certin stuff gets absorbed in different parts of the intestines and vitamins are the very last to go at the end of the small intestines ...I had 9 feet[small] removed and 3+ of large....Im doing as good as I can... So I wouldnt worry about that very much ,there are injection the doctor can give [It feels awesome , you feel alive, atleast when I get them , not sure if all feel it....You may also be anemic [low iron] another one thats makes you feel weak ,tired.......Good luck..Rod.I had a blood test for some other reason that showed low B12, that the doctor didn't think was important, and about the same time in my life started getting lower right pain that was put down to IBS. Many many many years later (about 17) my "IBS" got worse and I was eventually diagnosed with Crohns. A blood test then showed low B12, and I read somewhere that the terminal ileum (where my Crohns was) is where B12 is absorbed... and the penny dropped.
So I think I probably had low B12 that whole time. I think the main symptom was simply depression, as since I've been getting injections I don't feel that way.