Check out the support groups on Facebook. “ Pernicious Anemia & B12 Deficiency Support” is the best one I’ve found to explain how PA works and is diagnosed. One test—intrinsic cell antibodies—showed that my guts cannot use oral B’s. They just circulate in the blood. Tests seem low normal, but symptoms persist. The only treatment is B12 injections for life, along with supplemental cofactors that allow it to be used.
I also have kidney disease, and heart and autoimmune problems, but injections help. Best wishes for you!