Thyroid UK
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B12 Deficiency or Hypothyroidism?

I know everyone keeps playing the guessing game but I still can't figure out if I am suffering from B12 deficiency or hypothyroidism. I am having memory issues along with cognitive decline and am still quiet far from a diagnosis. I tested for AMA antibodies (Anti-TPO) and they came out at 122 IU/ml (negative for < 34) . My TSH is at 6.7 and B12 was at 180 hence I have been supplementing with methylcobalamin for the past 8 months with my current b12 level at 1000+. My question to the experts here is whether a 6.7 level TSH cause brain fog/cognitive issues without any other visible symptoms for hypothyroidism? Also how does one arrive at the diagnosis of B12 vs thyroidism?

4 Replies


It is possible you are hypothyroid and B12 deficient. Primary hypothyroidism is diagnosed by having TSH over range and B12 deficiency will be diagnosed by having B12 level below range.


Good morning Dlonleyguy,

I have both and symptons especialy the brain fog did not start to clear untill I started getting treated for both.

Perhaps it will be the same for you ?

kind regards



You've got both. Now, B12 levels can be misleading. How much B12 are you taking and how often?

Are you on any thyroid hormone replacement?


Thanks guys for the responses. Well I am taking 5000 mcg daily (Jarrows) and the GP hasn't started with the thyroid treatment yet. Not Sure if I need thyroid replacement at 7 TSH. Also does the high TPO count mean I have Hashimotos for sure or could it be elevated due to some other reason as well?


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