Pernicious Anaemia Society
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Reaction to b12

Anyone understand severe reaction to B12 injections and sublingual B12?

Hi, I've felt ill for years and extremely ill for the past year. Eventually in June 2012 I agreed to see a phychiatrist as my gp said there was nothing physically wrong with me and that I was suffering from major depression. I wasn't depressed. The phychiatrist said I wasn't depressed but did serum b12 test as I had symptoms of b12 deficiency including nerve problems . The test came back at 170 . I think then my gp did some sort of other blood test which showed that my red blood cells were normal. He said that he found it very hard to believe that I my symptoms were caused by b12 deficiency as I didn't have b12 anaemia. Eventually he agreed to the b12 shots. Five minutes after I had the first one I started shaking uncontrollably and had a terrible pain in my jaw and chest. It wore off after a couple of days. The following week after my injection I had the same reaction but much worse. I went back to my gp the next day. My blood pressure was high but he told me more or less that I had a mental health problem because a vitamin can't cause a reaction like that. I asked him a few days later to check my electrolytes. He did a blood test and said they were fine. The reaction wore off after a week and alot of my symptoms caused by low b12 improved for about three weeks. My gp refused to give me any more b12. I bought some jarrow b12 sublingual but even small amounts made me shake uncontrollably and it felt like I had tons of adrenaline. 6 weeks later I insisted I needed it looking into and he said he would so long as my b12 levels were still low. They came back at 400 so he won't treat it. 2 weeks later I became really ill. I saw another gp as mine was away and she said I have sjogrens syndrome. I probably do and it seems it can cause b12 deficiency. I have had a 3 month wait and will see a rheumatologist in 10 days and hopefully get some help. Once I've started seeing the rheumatologist I intend changing surgeries. I've pleaded with my gp over the last 6 weeks to change it to an urgent referal because I didn't feel that I would still be alive for the appointment but he said he couldn't. I have the worst phobia imaginable of hospitals otherwise I would have been in a and e numerous times. This is a huge problem because I couldn't face going when I really felt I was desperately ill after having the b12 injection. I'm sorry for the extremely long post but wanted to get as much detail in as possible Anyway anyone with an understanding of severe reactions to b12 or any other suggestions would be great. Thanks in advance and best wishes to everyone.


10 Replies

Hi Carmel...I would seriously seek a second opinion from another GP if I were you. If not B12 deficient it could be something which has similar symptoms. Please go and see another GP. Wish you the best of luck, you must be going out of mind. Michelle


Carmel, I had the same reaction you describe: "Five minutes after I had the first one I started shaking uncontrollably and had a terrible pain in my jaw and chest. It wore off after a couple of days."

I was diagnosed with Pernicious Anaemia last year, all my symptoms up to then being blamed on hypothyroidism. For years I had nerve-damage and loss of sensation, paralysis and even irretrievable loss of hearing (now have 2 hearing aids). My B12 levels were ALWAYS low but not low enough until the reference range was altered last year and I suddenly became described as severely and dangerously deficient. I was put on a series of 6-shot loading doses almost immediately.

20 minutes after the 1st one, I was shouted at on a bus by a man who tried to attack me. Suddenly I felt a pain in my chest like I'd been punched, felt very dizzy and made my way to the exit to get off the bus as I thought I was going to faint. I couldn't feel my legs and fell onto the pavement where I started to shake all over and have what witnesses described as like an epileptic fit. I was fully conscious throughout, but couldn;t stop my arms and legs fliling and twitching uncontollably. I also couldn't breathe as the chest pain was overwhelming. A passing ambulance crew stopped and sat with me but I didn't go to hospiyal as, once I was able to breathe and regain my composure, I felt OKish. The pain in my legs didn't subside for a couple of months...

I went back for my 2nd injection a few days later and told the nurse what had happened. She reassured me it had been purely coincidental and was more-likely a panic-attack reaction to the incident on the bus. The pain and breathing problems were because I was so severely B12 deficient. No-one else had reported such a reaction,,, so, over the next fortnight I had the 2nd injection, and the 3rd, 4th and 5th. EVERY time I suffered a worsening in breathing problems and the familiar chest cramp and cramping in the legs. Each time the pain worse off a bit quicker, so I risked the final jab.

To be honest I didn't initially feel any improvement to my health and was, in fact very worried that I'd been left with severe pins and needles and tingling, burning skin. My rosacea worsened and I had a pronounced butterfly rash across my face. Small itchy scabs affected my scalp (fortunately not headlice, though it felt just like it), and some of my hair fell out.

I was due further jabs in November and next month but my GP has stopped them until my Vitamin D deficiency is fixed. My thyroid mediction stopped working for me and my TSH is now through the roof, so he's addressing that too. GP says that he'd never heard of anyone having the reaction I described and that I'm "One of those people who reacts to everything"! (I have had recorded reactions to vaccines, antibiotics and other medications, so he wasn't being sarcastic)

Fortunately, at the moment, although my blood results are the worst they've ever been, a lot of my neurological symptoms have gone. Before I had the B12 injections, I suffered from breathing difficulty, even stopping breathing in my sleep, numb toes and fingers, and random muscle tics which would last for weeks on end. Even my balance problems have eased! This all seems to be a positive result of the B12 injections. The side-effects from the jabs have now all gone, thank goodness - at one point I was convinced they'd damaged me for life...

I really do not know what the answer to this is apart from reassuring you that, yes, it is possible to have the reactions you had. I had them too and it was terrifying. For some reason, these rections are so rare as to not be recognised by the medical profession or any of the pharmacists I asked. The answer they gave me is not good enough, ie- to just not treat the B12 deficiency, if the treatment makes me so ill! For me it is not an option, as I WILL end up disabled. :o(


Hi, thanks so much for your replies. I'm hoping that when I see the rheumatologist that they'll refer me to a neurologist or haematologist who may understand b12 a bit better than my gp. Also will then change surgeries as I don't feel I can continue seeing my gp.

I'm so sorry that you had a bad reaction lemurtail, it sure is scary. I've also had reactions to multiple antibiotics and actually the majority of medications. I forgot to say that I felt too weak to stand up for a week after, the second injection and also a bounding heart which my head nodded in time with. ( very strange ). The last few months I have bouts of what seems to be rosacea in the butterfly pattern and what looks like cradle cap. Do you know if these are related to lack of b12 ? I also now have a vitamin d deficiency and my whole body including mouth, nose, ears, nose and skin have dried out which is why they are sending me to the rheumatologist with regard to sjogrens. I don't know though. I just feel like I may be dehydrated. I have to drink bucketfuls of water. ( I've tested negative for diabetes ) one of the gp.s at my surgery says I have all the symptoms of thyroid problems but I tested negative for that.

It's funny that we have alot of simalarities. At least your gp believes your reaction. It seems any time mine doesn't understand something about my health he decides that it's all in my mind.

Thanks again for taking the time to reply



This is possibly caused by having low potassium and usually those who must have B12 injections fare better if they make sure that they have a high potassium diet, on the PA society site people are often warned about this, usually the recommendation is to eat bananas as they are high in potassium. it has something to do with the B12 being used by the body almost immediately to make the red blood cells it needs (B12 anaemia ) badly and so the potassium reserves are depleted.

You can read something about this at this link:

More can be found out from the pernicious anaemia society site, where you will find a weaalth of information.

Joining also gives you access to their telephone helpine where you can discuss problems with a medically qualified adviser. Much of this website is open for all, including the excellent and informative forums, plus the downloads. These were invaluable to me when self-dealing with B12 deficiency symptoms doctor would not recognise.

Carmel, it is recognised that having a B12 deficiency will not necessarily demonstrate anaemia by the enlarged cells, because of other body chemistry, but at least you are now getting treatment. You can read all about PA/B12 deficiency in these books:

Pernicious Anaemia: the forgotten disease. By Martyn Hooper. Martyn has PA and started the PA Society which must by now have saved or improved many lives, including my own.

Could it be B12? By Sally Pacholok and Jeffrey Stuart

Lemurtail,I am puzzled by your intiial treatment which does not seem to be inaccordance with the doctors' bible: the British National Formulary.

It says, Section 9, Nutrition and blood, subsection 9.1.2 9.1.2, under Hydroxocobalamin.


By intramuscular injection, pernicious anaemia and other macrocytic anaemias without neurological involvement, initially 1mg 3 times a week for 2 weeks and then 1mg every three months.

Pernicious anaemia and other macrocytic anaemias with neurological involvement initially 1 mg on alternate days until no further improvement, then 1 mg every 2 months.

i hope this helps.

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Thanks for the information on potassium and B12. I've done a lot of research in my effort to better understand my PA, but somehow missed that. I did find that the link did not work for me; here's one that does:


Don't know why the link isn't clickable, but copy/paste works.


Thankyou very much for your answer. I had read about the pottasium and persuaded my gp to check my level when I was having the reaction. He said my level was fine but I wonder if the serum test for pottasium is accurate as I did have the symptoms of low pottasium.

I've a week until I see the rheumatologist but the more I have read about b12 deficiency the more I think that all of my symptoms are caused by b12 & nothing else. My mouth is such a mess that it's nearly impossible to eat or drink anything apart from water. The muscles on my arms are agony and wasting visibly daily. I might try eating lots of bananas and trying the sublingual again. Just to get me through until I see the rheumatologist.

I can't wait until I can join the pas but embarrassingly I have huge money issues since I became ill and cannot find the funds to join yet.

Again, thankyou for all your help.

Best wishes



If there was an effect on potassium then it coudl be transient - only detectable at the time you had the bad reaction, not at a later date.

I've had a bad reaction from a fairly low dose of iron supplements. To say that vitamins and minerals can't cause adverse effects is daft. In very deficient people I think it can make a huge difference.


What do you do if you need iron and b12 but are allergic to both?


Thankyou poing.


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