What tests, etc. did your doctor run when you got diagnosed with Celiac?

Hi, this is my first post here. It's probably a bit off-beat. A bit of background. I live in Japan (but am not Japanese). I went to the doctor recently, and the outcome was that he suspected maybe Celiac. The problem is that he then went on to explain that Japanese simply do not get Celiac disease. It doesn't exist in Japan, so they have no way to test and its not covered by insurance and they can't do anything to help.

So, I am going to go and see a doctor back in my home country next time I'm there, but in the mean time I was wondering if people had any advice about what your doctor told you and what tests they ran when you were diagnosed. From looking around online it seems like vitamin deficiencies are common (or not?). Did anyone need supplements or injections or other things? I feel like I am in a bit of limbo because my symptoms have definitely improved after stopping wheat, but I've also read that you need to keep on consuming wheat if you want to get a proper diagnosis.

Edit: Thanks everyone for your answers. It has been really helpful! I'll get straight back onto gluten until I see the doctor, because a definitive diagnosis (if possible) would be good.