Pernicious Anaemia Society
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Advice to supplement

I have underactive thyroid and have been feeling quite unwell (particularly v tired) for a couple of years and thankfully just found the thyroid UK website where I have had advice. I've started to take 5,000 Vit D3, K2 and magnesium a couple of weeks ago.

They suggested asking PAC for advice regarding B12 supplements.

I have also just received a referral appointment with an endo next month.

My full results from blue horizon were:

TSH 0.2. (0.27-4.2)

T4 Total 112.9 (64.5-142)

Free T4 17.16 (12-22)

Free T3 3.74 (3.1-6.8)

Vitamin D (25 OH). 62 (Insufficient 25-50)

Vitamin B12. 314. (Insufficient 140-250)

Serum Folate. 23.11. (8.83-60.8)

CRP 3.8. (<5.0)

Ferritin. 93.6. (20-150)

Anti-Thyroidperoxidase abs 14.7. ( <34 )

Anti-Thyroglobulin Abs. 11. (<115)

Any advice appreciated


2 Replies

people vary a lot when it comes to B12 - this means that just using serum B12 as an indicator will result in missing 25% of people who are B12 deficient but also picking up 5% who aren't.

Having said that though your chances of being one of the 25% who are deficient gets lower and low as you get into the normal range and actually your levels are well into the normal range - though still in the grey area

Using symptoms as a guide is going to be difficult if you have an existing thyroid problem and that isn't under control.

tests that can help clarify on a B12 deficiency are homocysteine and MMA - both of which will be elevated if your cells don't have enough B12 to recycle them into useful building blocks.

I personally wouldn't recommend supplementing B12 - certainly not with high doses of B12 (1000mcg+) unless you are really sure that you have a deficiency caused by an absorption problem and have exhausted every possible avenue for getting a formal diagnosis - at best it is a waste of money and at worst it could kick of another reaction that will leave you needing to maintain serum levels much higher than they would otherwise need to be.

Possible absorption problems include - PA, Coeliacs, Crohn's, h pylori infection, and various drug interactions - including PPIs such as omeprazole, metformin used to treat type 2 diabetes, NSAIDs, some anti-epileptic medications (which can be used for other things).

Your folate looks reasonable.


Thanks Gambit62. As I now have an appointment with an endo next month perhaps its best to leave B12 supplements for now.

I do have symptoms but these may be caused by thyroid. Its become progressively much worse over the last year or so. It's mainly the brain fog that is concerning me at the moment as I Was finding it difficult at work to concentrate and have just changed roles a few weeks ago and struggling with the new things I have to learn. Also the tiredness and lack of energy is so bad but hopefully Vit D supplements will help.

It's frustrating that it takes so long to get to the problem and fix it.


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