Pernicious Anaemia Society
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Side effects?

Please can you help? I suffer from b12 deficiency and I take sublingual lozenges and it seems not too bad. My mum has recently been diagnosed, has really bad symptoms but she is getting horrible hypersensitivity from first of all the one injection she had a few days later. Now taking 1000 solgar sublinguals a day after a couple of days starts the symptoms which are dizziness and really bad hayfever like nose and eyes running and sneezing? She cannot do without the vitamin obviously but she cannot have this going on either as she can not go anywhere with it.

Can anyone make any suggestions as to why this is happening and what she can take for the deficiency. The injection was hydroxycobalamin and the lozenges are methylcobalamin.

thnks in advance.

She is worried that it is the site that her brain tumor was removed from causing her dizziness from the tablets in some way. I said I doubt it but could she be right?

8 Replies

Lack of B12 slows down a process called methylation, which affects many things, including the immune system.

People have different reactions to supplements depending on what else is going on in their body at the time. If your mum has been super deficient in B12 for a long time, then taking large doses - such as you find in an injection or in 1000 mcg tablets - can be too much all at once. Your mum still needs the B12, but she needs to take it more slowly to give her body time to adjust to things. Can you cut up the tablets or get something containing a smaller dose?


Hi Ladydawny

You state your mom has been diagnosed, but what does that really mean in real terms, what tests have been performed exactly. You also imply that your mother has undergone surgery for a brain tumor, if so, then that could possibly be why your mom is deficient in B12, due to the possibility of the anesthesia containing Nitrous Oxide. First I feel you should inquire what tests your mom has had, then you will have a better picture with regards to the best way forward.

I also agree with Poing, it is also possible, that your mother following injections, suffers from a condition known as a B12 overload. Depending upon the tests / results etc. I would think your Mom should return to her Consultant in Oncology and explain her problem in detail. I also note that your Mom has started taking Methylcobalamin in lozenge form, how long after her injection did she start this course of self medication, which in itself, is not a good thing to be doing, especially without both the test results and a full understanding of their meaning. The injections are normally 1000mcgs of Hydroxycobalamin and are again normally given every 3 months once the progarm is under way. However, in the beginning GP's will often begin with weekly or even daily doses. If your Mom has added 1000mcgs of Methylcobalamin to a recent injected dose, then that too could be your answer.

Like everything about B12, sadly there are many questions and a complex enigma of answers to be understood.

Hope this helps, but do be very careful about self-medication, it can be a very dangerous route to take if you are not fully informed. Please get advice before you do anymore.

Best wishes B12 Turbo


Thank you very much for your answers. The immune system problem sounds interesting and likely.

She had the symptoms after one injection. Didn't return for the rest of the loading injections due to the side effects and I was worried about the deficiency so I gave her a dozen of my lozenges. I understood you only absorb around 20 percent of the injections and even less of the lozenges. She took these a couple of days apart a week after the needle. She is still feeling the b12 deficiency symptoms.

She could be suffering from the effects of the surgery anaesthetic yes, it was done in 2006 she could have been deficient a long time. She also had gammaknife for another tumour in 2010, these are benign but as you know no room for them in your skull.,

We asked for the b12 serum and intrinsic factor test, mum is often iron deficient also but takes iron when necessary..

The Dr did run an intrinsic factor but it got lost so she has to go for another. That's it really. Getting tested for anything on the NHS is like pulling teeth. Treatment for many things lately seems bad too, especially chronic illnesses, and from what I am reading for b12 deficiency.

Poor mum, I seriously was hoping she could have the BNF recommended treatment and have some energy and feel more positive and less aches.

This worries me, I did not realize that b12 was dangerous as on the site they say you cannot overdose with it.

hugs Dawnx


Sensitivity/allergy to B12 itself does happen but it is extremely rare. And no, you can't overdose on it. There is a danger of low potassium levels when you first start treatment, so potassium should be monitored and you should eat lots of potassium rich foods.

Just an observation, but it is extremely common to feel worse when you first start B12 treatment, before you feel better. Particularly if you are also low on folate and iron and these deficiencies haven't been addressed. These are called start-up symptoms or detox symptoms. Here is a link about this:

It really would be best if she could get the injections under a doctors supervision, perhaps more spaced out? Find out folate, ferritin and potassium levels as well. Also wondered why you weren't on injections either?

H x


I really don't know what to say to my Dr about my health any more. I tested low on B12 but not below range, low folate, low zinc, low iron, low vit D. I also have Hashimoto's disease and I am housebound. My doctor doesn't know what to do with me. I am having a test for addisons disease soon. All I really got from the doctor was one months folic acid and Ievothyroxine. I gave up on doctors about 10 years ago when I was laid on the sofa without the energy to even breathe properly and they did nothing because at that time apparently all my bloods were normal. They didn't test my nutrients though. I am now on a gluten free diet and pretty much had to learn to manage my own health as best I can.


If you fancy it there's a Facebook group here for PA/B12d lots of sufferers in the same situation as you who have had to look out for themselves:

And the PAS forum (which you can read without being a member):


H x


Thanks ever so much, I shall most definitely make my way to those links.

take care



Thanks so much for the info and the links folks :D



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