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Pernicious Anaemia Society
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Possible reaction to b12 injection?

I believe I have been under treated for pernicious anaemia for many years and last year decided to try self injecting.

I decided to go with sub cut as I figured it would be easier.

I noticed I felt quite unwell for a few hours afterwards and it put me off so didn't bother again but I feel so poorly I do feel like I need more b12.

I decided to try again this time

Doing intramuscular with the help of my friend who was a nurse.

Straight after she did the injection I felt really weird as if I had loads of adrenaline running through me.

I felt weak and shaky.also flushing i my face.

I still feel a little wonky now although not as bad.

I got the b12 fr Germany as suggested by somebody on the forum.its b12 depot rote medica hydroxocobalamin

I was just wondering if you can be sensitive to different brands of hydroxo?

I've been having my injection every three months for the last 14 years and I've never had a reaction.

Any help would be much appreciated.

7 Replies

I can get hot and flushed, tired, headachy some 4 hours after B12 injections, I think its the body being busy with doing things with the newly added B12, its only one day in my case, next day I feel very well. I do not know if a different B12 preparation would given you different side effects, it can be a different preservative and or your body being more in need of B12 etc. If its unpleasant the next day I'd think again, but one day of feeling a bit off after a B12 jab seems normal to me..Marre.


I have had a similar reaction. My nurse at the clinic suggested taking anti-histamine, it helps. If you get a throat closing swollen lips and tongue, go straight to a & e.

Hope it goes well for you, take care.


methylcobalamin is the best form of b12 injection and can be purchased from oxford biosciences in GB the difficulty then is that health care provider will only prescribe hydroxocobalamin ------------- you could try a lower dose IE half an ampoule and see if that improves your situation you could then build it up to the full dose


Thanks for your replies.

I guess what I can't really fathom out is why I have had a bad reaction to the hyroxocobalamin when I've been having them for 14 years with the nurse at my surgery and never have any problem after what so ever?

This is why I wondered if different brands may put slightly different ingredients in and perhaps there may be a different ingredient in the one from Germany and that's why I had a reaction?its really perplexed me.


Certain brans of B12 do have different preservatives in them, so there may be a difference, do you know what you got from the surgery, know what was in it? You them can compare it with what you have bought from Germany. But it can also just be that you were more in need of the B12 so felt the reaction to having more B12 more or just a nervous day..


Thanks marre

I will try and find out which brand my surgery uses. I also have lupus so my immune system is very sensitive which may have over reacted to some different ingredient than body is used to perhaps.

I am seeing a private doctor next week who wants me to try the methycobalamin.

I like the sound of this form as it sounds more natural.

I did try taking sublinguals a few years back.

I found that my serum blood b12 levels raised but I didn't feel any improvement in symptoms although at the time I was unknowingly very low in folate and ferritin which I am now taking supplements for.

I have heard some people find that the sublinguals don't seem to work for them and only find relief from injecting so its possible I may fall into this category.


Hi lottiex,

Different people react differently to different forms of B12, injected or not, cyano, hydroxo and or methylcobalamin, so its a matter of trail and error to find what suits your body best! Same counts for different forms of folic acid etc. And yes important to have also good levels of folate and ferritin for the B12,

Kind regards,



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