I had lots of symtoms of B12 deficiency, I have a family history of underactive thyroid and PA, I have an underactive thyroid. In Oct 17 my B12 levels came back in the normal range but I tested positive for pariental cell antibodies. Armed with loads of information from this site my doctor agreed to a therapeutic trial of B12 - I received 5 injections over 5 weeks. Today after discussing an improvement in my symptoms he has agreed to injections on a 3 monthly basis. Thank you to all who contribute to this site, I have come out of a fog and everything seems brighter again.