Low Vitamin B12 & Under active Thyroid - Thyroid UK

Thyroid UK

130,634 members153,924 posts

Low Vitamin B12 & Under active Thyroid

Schristie1992 profile image
17 Replies

Hi everyone.

I was at the doctors today and my Levothyroxine has been increased to 50mcg as my TSH level has went from 1.3 to 5.51.

I've also had problems with my eyes for 12 weeks (since i was diagnosed as under active thyroid). I've posted before asking for advice as they are always puffy,swollen,dry and red. Doctors prescribed me Eumovate (a strong steroid) and Hydromol ointment and an antihistamine a month ago. They seem to be working but I am having to use the steroid cream every few days, and your not supposed to use this long term as it burns a layer of your skin.

My main concern regarding my blood results today is that the doctor was very concerned, my Vitamin B12 is very low. It should range between 200-600 and mine is 107. The doctor doesn't understand why as I have a varied diet. I was glad to have this diagnosis as it explains why I am permanently exhausted but do you think this could be why I'm having problems with my eyes? I have been prescribed Hydroxycobalamin injections that I have to get every 2nd day for two weeks and then I'll have some more blood tests done and most likely be put on an oral supplement. But the doctor said because its so low he may have to refer me to Hematologist. I'm very worried about this and feel my body is just deteriorating.

Has anyone else had very low Vitamin B12 and underactive thyroid?

17 Replies
shaws profile image

Unless you are very frail with a heart disease, the starting dose should have been 50mcg with an increase of 25mcg every six weeks until your TSH is 1 or lower. I do know many doctors believe that 'in range' is fine for the TSH but that isn't right and they are poorly trained about dysfunctions of the thyroid gland.

If your B12, Vit D, iron, ferritin and folate haven't been tested ask for these the next time. Are you aware of the procedure for getting the best result out of blood tests, i.e. the earliest possible time, etc et.

Schristie1992 profile image
Schristie1992 in reply to shaws

Hi shaws,

Ive been telling the doctors for months I need an increase and they have only just done that today. Ive been taking 25mcg since I was diagnosed and just increased it to 50mcg today.

Ive just had my test results also today for B12,Vitamin D, Iron, ferratin and folate and B12 is very low, 107.

I always fast for blood tests :)

Nicole1027 profile image
Nicole1027 in reply to Schristie1992


I was reading your post and wanted say that my doctor started me on 25mcg of Synthroid and kept me on that dosage for way too long!!! I started having bad side effects until I reached out to someone on this website who let me know what to do. I was on 25mcg for 3 months when my dosage was supposed to be increased in 6 wks.

When I finally went back to the doctor he only increased my by 1/2 tablet for a total of 37 mcg!! Which still wasn't helping!! I am done with traditional doctors! I am now in the beginning stages of treating myself and this will also help me to save money that I have thrown away on doctors. I just recently ordered NDT from thailand and waiting for it to arrive. We all have to take charge of our health!

shaws profile image
shawsAdministrator in reply to Nicole1027

I much prefer self-medicating due to the fact that I have become well again.

Also on the forum when we learn that there are options of thyroid hormone replacements instead of the 'one size fits all' (i.e. levo) comes as a surprise. Of course many do recover their health on levo which relieves their symptoms (I have met people who have had no problems with levo) but for those who remain unwell and have a life of difficulties because doctors hands are tied as they've had to do as they're directed. Also there is the danger that these patients might develop other more serious conditions due to not being on an optimum dose being restricted due to the TSH being in range.

shaws profile image

He should do an intrinsic factor first before you get B12 injections to see if you have another autoimmune disease which would be pernicious anaemia.

So don't take B12 supplements or injections until you've had this test taken.

You can also post on the Pernicious Anaemia Society in Healthunlocked for more information. You can either have P.A. or a B12 deficiency. P.A. is a lifelong condition with regular B12 injections for life.

SlowDragon profile image

Your GP should have tested you for Pernicious Anaemia with such a low result before first injection. Did they do that?

Have you had thyroid antibodies tested? If not request that they are

Standard starter dose is 50mcgs. So it's hardly surprising you felt terrible. A tiny dose reduces thyroid output and does not give enough in replacement.

Dose should be increased in 25mcg steps until TSH is around one and FT4 towards top of range

Low B12, folate, ferritin and vitamin D are extremely common when under medicated

If you have high thyroid antibodies this is Hashimoto's also called autoimmune thyroid disease. It's likely as 90% of primary hypothyroidism is due to autoimmune thyroid disease

Essential to know

Schristie1992 profile image
Schristie1992 in reply to SlowDragon

The GP didnt test for Pernicious Anaemia as he is aware its more common in people over 60, Im 25. After the injections he may refer me to a hematologist.

SlowDragon profile image
SlowDragonAdministrator in reply to Schristie1992

I suggest you ask about this on PAS healthunlocked- they are the experts on PA

I would agree with SaggyUk, and thought testing for PA more likely if young, not less



Clutter profile image
Clutter in reply to Schristie1992


Being more common in people over 60 doesn't preclude younger people having PA. Your GP should do the requisite tests to check. The PAS forum can help you with what you need to say to your GP.

Schristie1992 profile image
Schristie1992 in reply to Clutter

Thank you. I’ve put a post up, no replies yet 🙂

shaws profile image
shawsAdministrator in reply to Schristie1992

Your doctor like many other doctors who are treating patients seem not to have a clue about the seriousness of below range Vit D and Vit B12 - these are not strictly hormones but pro-hormones and for B12 in particular (I was diagnosed in my 40's by a good doctor who wondered why my blood looked a bit strange). I then said my mother had P.A. and I was promptly sent for a test which came back positive. So I was fortunate to have no clinical symptoms at all as I had seen the doctor for other reasons. Very low B12 can lead to dementia as well as lots of other things. This is an excerpt. We have to read, learn and ask questions if we want a healthy life, free of clinical symptoms where possible:-

There is a growing relationship between multiple sclerosis, which involves the disintegration of myelin and brain white matter and vitamin B12 deficiency. Finally, B12 is involved in approximately 100 functions including DNA, RNA, hormone, lipid and protein synthesis.22 Aug 2013

Are You Vitamin B12 Deficient?- Hormones Matter


Greybeard profile image

Your doctor isn't doing a very good job for you. It shouldnt be upto you to check their every move and pay for their inept treatment with your health. Plenty more fish in the sea.

Saggyuk profile image

Hi there

No he was wrong, he should have tested you for pernicous anaemia.

My thyroid wasn't tested for 7/8 years because they believed I was too young to have thyroid problems but anyone can have it and doesn't mean you shouldn't be tested. Problem is pernicous anaemia is an autoimmune disease much like thyroid and if you have one autoimmune disease, you're more likely to have another. Plus if you do have pernicious aneamia, you will need the injections for life so not knowing and not continuing with injections will put you stright back where you are now before long and B12 is the worst deficiency in my opinion as can cause irreversible damage

If your other nutrients were at good levels, that would be even more reason to suspect pernicious anaemia.

What were your other levels as docs often not so good with nutrition and often don't read results well so would be well worth posting them too.

You should also retest for iron deficiency in three months if your B12 is then good as B12 deficiency can falsy elevate ferritin and mask iron deficiency in some cases. My mum had this issue.

On the plus side, this would have been making you feel absolutely terrible so you should feel much better soon :-)

Schristie1992 profile image
Schristie1992 in reply to Saggyuk

Thanks Saggyuk. I have been awful but put it down to thyroid as doctors don’t test for B12 if no reason to! I always feel very awkward because doctors are supposed to know best and we trust them with our health and I don’t really like querying their judgement. I will push for perinicious anemia test though. I didn’t actually get a print out as I was very upset. How do you mean b12 deficiency can cause irreversible damage?

Saggyuk profile image
Saggyuk in reply to Schristie1992

I know and I wish I could say it was true but many of us here on the site are here because their docs left them ill and in an awful condition.

Anyway - here's a link to the NICE guidelines which are the ones they are supposed to follow and it quite categorically states to determine the cause of Low B12. If your diet if varied and not starving yourself or a vegan, then the cause should be determined including testing for pernicious anaemia. The other likely cause can be stomach conditions which prevent you absorbing all nutrients such as Coeliacs and other inflammatory bowel conditions in which case you should be referred to a gastroenterologist.


You can show him this if necessary to ensure you get the testing. It also explains how you should be treated - which is not as simple as just two weeks so have a read.

Here's some info on the condition.


Here's a video of some of the worst case scenarios - this isn't to scare you as is worst case scenario (and contains of lot of info you need to know whether PA or not) but it's so you realise that it's really important to push the doc to get to the bottom of it if no obvious cause as you may be relying on the doc for those injections.


In many of us, it is often more likely to be stomach issues which can be resolved if stomach issues are resolved or supplemented but PA needs to be discounted as even supplements for B12 are likely not to be absorbed.

SlowDragon profile image

You MUST also INSIST on Thyroid antibodies test.

Most likely your B12 is due to hypothyroidism, but you need to establish if it's autoimmune thyroid disease (Hashimoto's) by testing antibodies

Perhaps take a supportive friend or family member along with you

Saggyuk profile image
Saggyuk in reply to SlowDragon

Yes apologies, it can also be caused by hypothyroidism - forgot to add that bit :-)

And def need to to get antibodies tested.

You may also like...