Thyroid UK

Is it worth checking antibodies for B12 deficiency?

Hi all,

This is my first question though I've been reading a lot on here the past few weeks. I wish I'd joined sooner- it would have really altered my decisions this past year..

I found I was really tired last year so after some thinking asked my doctor to do a thyroid check and came up with a TSH of 4.5 (0.3-3), low normal free T4. Positive antibodies so managed to persuade my doctor to trial me on levothyroxine. Some hiccups along the way but I'm currently on 150mcg a day, hoping it's the right dose!! Just moved up from 100mcg, TSH 2 weeks ago was 4.0.

Anyhow, earlier this year I also found I was vit D deficient and my ferritin is always scraping along the bottom of the reference range. Trying to manage these myself, I requested copies do all my bloods and noticed my total B12 had fallen from 450 to 312 over 6 months. Docs didn't seem concerned so I had an active B12 test done by Blue Horizon. The result was 56.7pmol/L (25-125). At the time, I read something that said 25-50 was the grey zone where further investigation might be done so didn't pursue anything because I was above this.

However, I've since read that anything less than 70pmol/L should be investigated. Unfortunately, I've been taking sublingual b12 10000mcg daily for the past few months. I can't bear the thought of stopping them as I'm just about getting by at the moment. I would really like to know, though, if it's PA or just deficiency. Would antibody testing be worthwhile at this stage?? I know the treatment is the same but I also know PA sufferers are at increases risk of gastric cancer so would like to have the correct monitoring in the future. It would also be good to know if this is a for life thing or whether I could scale supplements back. I'm taking something like 15 tablets a day at the moment for everything; it would be good to cut back!!

Sorry this is so long-winded; I just wanted to include what I thought was relevant.

Many thanks in advance :)

8 Replies

This is from the Pernicious Anaemia Society for information:-



Ickleitcrazy, The increased dose should bring down your TSH which is still very high and will increase your FT4 and FT3.

Hampster1 is the forum expert on B12, folate and PA. You can search her username or search B12 or pernicious anaemia.

1 like

...I don't think hampster1 is with us still. I really miss her :-(


Marz, No, she deleted her account. I think she posts on


..yes she gave me the link before she left but I do not do Facebook :-(


Have you also gone Gluten Free ?

Its ferritin which must be over 70 in order for your body to be able to convert levothyroxine T4 into the t3 your body needs

Its the effect of the hypothyroid which drives down feritin, folate b12 etc long before idiot doctors diagnose the hypothyroid

1 like

Thanks for your help. I've actually found my answer by searching through the website where there's a review of treating B12 deficiencies. It states that IF antibody results are unreliable if serum B12 levels are >295 so supplementation will certainly affect that.

Not to worry, I'll just carry on supplementing and keep an eye on everything and try and balance things as best I can.

Reallyfedup - I went to see an endo once after diagnosis; found him to be entirely unhelpful. He did check for coeliac disease though and I was found to be negative so I don't think gluten should be an issue for me.


The Coeliac test can be a little unreliable and is not in depth. Cyrex Labs in the States did a far more in depth test. This is now available with Regenerus Labs in the UK. Anyway going gluten free may help to heal the gut - which could possible be the source of your Hashimotos...

Check out Datis Kharrazian too :-)


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