Two things to check for with MRI. I had nothing wrong until car accident, hard shock up right side. I lied, I was a poor diabetic patient playing games w/Dr. then had car wreck. Trauma induced Neuropathy is a real thing. Good Luck, Ken in Texas.

I bought the B12 but haven't taken much. Didn't think it would make much difference.
I will start tomorrow morning! thank you so much!

but may not be bad enough to be symptomatic. Mine was 119 at one point and didn't have symptoms until I had a small car crash. I believe that Metformin taken over time can block b-12 absorbtion in a certain percentage of people. I am thinking one-third. So in my book that means if you take Metformin you need to know what that number is. I took shots monthly plus pills and felt improvement over the course of 5 or 6 mo. Good Luck, Ken in Texas.

I question the diagnostics. I've read that everyone in the 300's should be tested for pernicious anemia. I asked the hematologists about it. He did nothing. I regretfully didn't pursue it. I even developed vitiligo while taking b12. The vitiligo stopped when I started the methyl b12. It's so painfully obvious now. I'm with you about monitoring. I don't trust the results of conventional tests after my experience.

--I think anything up to about 500-550 is suspect--at least if one is eating a diet with animal protein sources in it (vegetarians/vegans are very often affected by lowering B12 levels as they do not get it from diet and we cannot manufacture it ourselves; such people should definitely supplement).

There have been people who have been symptomatic of B12 deficiency even into the 600 range.

I suspect that the original normal ranges for B12 are set too low at that end. Japanese labs, due to the drug-induced B12 crisis that Mrs. D has talked about here, tend to set the low end of their lab ranges around 500-550, and many have no upper limit. (I also think the upper limit of some labs in the 900 range are a little ridiculous--if one absorbs B12 well on a non-vegetarian diet, or if one supplements, especially with a daily B-complex, one's readings are likely to be higher. My wife takes a daily B-complex with 125mcg of B12 in it and her levels are usually in the 1100's. I take methylcobalamin 1000mcg three times/week and get readings in the 1500's-1800's. This, of course, frightens uniformed doctors unless you explain it to them--if they're willing to listen.)

getting to 600, means you could be suffering from b12 toxicity, which can cause pn like symptoms. b12 is a complicated molecule and bacteria produces it

Neuroproblem---- could you please explain this post? Provide links if you can too.

At this time there is no upper limit to B12 levels, established by research.