Mine was diagnosed through a fecal test and other tests also.
I take enzyme replacement therapy (Zenpep) to digest my food and yes I do receive B-12 shits every month in addition to vitamin and mineral supplements. I also supplement with Orgain protein (and no I do not receive any remuneration for recommending it). I have chosen to avoid sugar as to avoid the additional medication to digest simple carbs. I am NOT diabetic, it just requires a different therapy to digest sugar/simple carbs. I am able to digest complex carbohydrates and I am very thankful to be able to finally have a normal life without fear of embarrassment due to daily diarrhea, fainting, and looking like a refugee!. It’s been a whole new world for me after so many years of misdiagnosis and misery. I now have good muscle development am now up to 102 lbs. I’m looking forward to actually being able to wear summer clothes w/o fear of embarrassment 🤗