Vitamin Deficiency

I have been told that I had several vitamin levels that were low.  Vitamin D, Vitamin B-12, and Magnesium along with a higher glucose level (30) and a low Thyroid level (total Thyroidectomy).  Aside from diet, is there any one thing that would cause all these levels to be low at the same time? I had a B-12 shot today and was told that I would need to take 2 more to get my levels back up.  Should I be looking at taking more of these shots in the future?

[caregiver222]

Yes. The one link may be gastrointestinal. You may be taking in these nutrients, but they are not being absorbed into the body. B-12 is a funny animal. Sub-lingual B-12 (with folic acid) should be sufficient once your levels are up to speed through the injections.