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Pernicious Anaemia Society
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Side effects of b12 injections

I have just had my 3rd b12 loading injection and have noticed I have a red rash on my lower legs and feet. has anyone else experienced this?

21 Replies

This would be best reported to your doctor very soon, allowing him/her to decide if this rash might influence future treatment choice, as according to the British National Formulary a rash can be a sign of hyper-sensitivity to some ingredient of the injected hydroxocobalamin. From the BNF, in Section 9.1.2

Side-effects: nausea, headache, dizziness, fever, hypersensitivity reactions (including rash and pruritus); injection site reactions; hypokalaemia and thrombocytosis during initial treatment; chromaturia.


Thank you for your info.

I see the nurse next mon. for my next injection, so I will speak to her before she gives it to me.

I have also been having nausea, headaches, and a fever/hot sweats, so it does look like I could be hypersensative to the B12.


Hello nostoneunturned

Thought you would like to know that I managed to get an apointment with my Dr. at 2pm today, and I am to stop the B12 injections. I am going to try the tablet form instead.


Thank you for letting me know, I'm really relieved you are stopping injections, did not like the sound of your reactions at all! Also very glad that GP was up to speed and took your reactions seriously.

I know a little bit about B12 as I had to dig myself out of a black hole created by my GP's total, complete and absolute ignorance which forced me to research B12 in order to save myself by self-treatment by tablets as GP would not treat despite serum B12 level being below bottom of range plus many symptoms, too busy bawling at me about "health anxiety" So I hope you do not mind if I ask just which kind of B12 will be in the tablets - cyanocobalamin or methylcobalamin?

As you probably know there are two very good books on B12 issues, one by Martyn Hooper, who started the Pernicious Anaemia Society, and who has PA, his book is "Pernicious Anaemia: the forgotten illness", the other is "Could it be B12?" by Sally Pacholok and Jeffrey Stuart. Well worth reading.

Keep in touch!


Hello nostoneunturned

I replied to hampster1 at the very bottom [ below ] and this may answer your question.

Thanks for your concern, I do appreciate it. I really do still awful today, haven't eaten due to the nausea, I only hope that these symptoms soon disappear.

I will let you know how things go, but like I said read my answer to hampster1 it will save me typing it again



I just started B12 injections and I was told to be very careful about contamination. So I use alcohol on my hands, my leg where I give the injection, and I even whip the top of the vial where the needle goes in. If the needle touches anything I discard it and get a new one. In my opinion you should see a doctor soon. If you have an infection from contamination, you need to take care of that right away. If it's a rash then you may be having a reaction to the B12. Either way, go see you doctor and find out what it is. Good luck.


Thank you for your info.

I see the nurse next mon for my next injection, so I will speak to her before she gives it to me.

I am also having some nausea, headaches, and feel feverish, so it looks like I could be getting a reaction to the B12 I felt fine after my first 2 injections.


Hi mark5177

I managed to get an apointment to see my GP today at 2pm. I am to stop the B12 injections. I am going to try the tablet form instead.

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I'm sorry to hear this Bowler. What tablets have you been prescribed? They would need to be a really high dose to make any difference, and even then, it's questionable how much will get through your stomach. You might be better on the high dose 5000mg methyl sublinguals.

Hampster x


I wasn't even offered any medication, and it was sugested that I could take over the counter b12.!!! He was also of the opinion that I wasn't that deficient at 226.

I am at the moment reading the b12 book, "could it be B12 " perhaps when I'm finished I will drop it off at the surgery for them all to read!!!

So I told the Dr. that I would sort my own tablets , and go to Amazon for the methyl sublinguals as the B12 site recommended when I contacted them several weeks ago before I started treatment. They also said "to combine it with folic acid and B6"

I actually saw another locum today, a different locum to the one who I saw who agreed to the loading doses.

Unfortunatly our surgery is going through several changes since our regular Dr's retired after 30 yrs, [ I think I told you all this ] and hopefully we will soon get a permanent Dr. and nurse, [who also is a locum.] The trouble at the monment is I dont know who I will see from one visit to another. So I have decided buy my own medication, and see how things go.

I'm not sure wether to let things settle re my nausea, headaches, dizzyness, and rash, before I start taking tablets. I haven't been able to eat today due to the nausea, so i dont want to make it worse by taking the tablets immediatly, although I haven't ordered them yet.

This is all a new ailment/illness to me, as I have been dealing in the past 14 years with GCA, and the long term use of steroids, which cause me side effects, so this is something I can well do without.

Sorry for the moan.



Doesn't sound as though you have the enlightened GP I thought you had, sorry. One thing for sure, when you have read "Could it be B12?" you will know more than the GPs with their complacent attitudes.

If you would like to know how I raised b12 from the depths below the bottom of the NHS range to over 1500 link is below, lot of posts there, and if you have questions then I'll try to answer them. You need to know your folate levels. if low in the range then folic acid supplementation will be needed simultaneously with the methylcobalamin sub-lingual tablets. You will need the methylcobalamin 5000mcg (same as 5mg) from Amazon, Swanson's or Jarrow's, (reckoned to be the best) and also emphasise potassium in diet (bananas, figs, unsulphured blackstrap molasses.)




do a combined folate and serum B12 test for £30. Convert myrios' pmol/L to ng/L if necessary by dividing the pmol/L by 0.738.

You will get there!


Hello again

I think as there is so much info from you I will have to print it off.

You certainly know a thing or 2. about b12.

My serum ferritin was a little raised at 178.

serum iron level 14

saturation iron binding capac. 59

iron saturation 24%

b12 226

serum folate 10.4

mean corpuscular volume 89

white cell count 11,8 a little raised

red blood cell distribution width 14.3

haemoglobin estimation 143

red blood cell count 4.76

mean corpusc. haemoglobin 30.1

serum TSH level 1.05

My potassium level has always been on the high side around 6 but this tiime it came back as 4.2

I hope I haven't bored you with all this info

I'm still wondering wether to wait a while before I start taking vitamin b12 tablets.

isn't it all confusing, thank God I found this forum,



Morning, bowler. There is info on how to interpret FBC results here:



Example of a blood test:


Hope links are OK! There is an "iron" page on the STTM site but cannot find link. search:


Higher ferritin levels can indicate inflammation but GCA is probably the source of inflammation. Ranges are needed to interpret blood tests with any accuracy as labs can differ in ranges used.

If you are stlll concerned about the effects of the B12 tablets perhaps it would be worth considering methylcobalamin in spray form? No excipients. Occasionally, in addition to the daily 5 tablets, I used Pure Advantage B12 500mcg spray, 175 sprays delivering 500mcg B12 per spray but higher percentage absorption per dose. I depended on the tablets mainly, absorption rate about 15-20%, having read K Byrne's "The Enterohepatic Circulation of Vitamin B12" available from the Pernicious Anaemia Society. Think K B's paper is for members only but worth joining PA Soc for lots of info.


K B explains about necessity of establishing a diffusion gradient for B12, basically higher level B12 outside cell than in it so B12 gets into the cells as flow is from high to low, and how to do this by ensuring large daily intake of B12, 25000mcg (25mg), you'll find a link within the posts accessed via my www.pasoc link above to how this is regarded by Dutch as equivalent of 2 injections weekly. My maintenance B12 is achieved by one day weekly intake of 3 x 5000mcg Swanson tablets plus dietary changes after reading Martyn Hooper's invaluable book (above).

CKS (Clinical Knowledge summaries) has info you might like to browse through:


Understand CKS might have undergone some changes recently so link might re-direct you.

You will be reading Pacholok's book with amazement at how medics can be so utterly blind. I know how blind they can be, I have been there, believe me, were it not for the internet and PA Soc.. B12.org I would by now be very, very ill, doc scratching head but happy to dismiss all symptoms as just "health anxiety". and "if you go looking for symptoms you will find them." Just who invents writhing facial muscles for the fun of it, or the umpteen other frightening symptoms I had? But my bitter experience has at least driven me to research, recover, help others via I/net for which I thank God. like you.

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I am so grateful for all your info, I have also had some from others on this site [ when I first posted.] so much so that I will have to print some off to read and absorb it all !!!

As i told you I have GCA, and have been taking steroids long term I also have high b/pressure [ caused by steroids ] which is affecting my kidneys, and I was told that kidney disease causes anaemia, so my jigsaw is coming together,

I am waiting to see a specialist at Addenbrooks, re my b/pressure, so I have a long list of questions for him!!!!!

You would have thought that with my symptoms the Dr's would have realised that having a low kidney function and a b12 level of 226 would have raised alarm bells, but Oh no, "I'm not deficient"

I'm just annoyed that I am allergic to the injections, however all is not lost with all the other stuff I can try, tablets, sprays, etc.,



When I had loading doses without folic acid (5mg) tab, I experienced headache and dodgy stomach, start burping etc, the reaction was almost immediate (within 30 mins or so) but I take 5mg folic acid everyday now and when I have an injection I do not experience these reaction anymore.


Thank you for your reply.

I'm hoping that when i start the b12 again. [ tablet form,] I will be able to include folic acid,

I am glad that you manage to tolerate the injections with the help of the folic acid.

it's strange how we all react differently to medication. I cant risk taking the injections again, especially with the headaches, as headaches are the symptom of GCA and I dont want a flare up of that.

Since stopping the b12 injection my rash is clearing, and no headache and fever, however I still feel a little nausea's, but at least things are improving.



I'm not suggesting go back on the jabs, but I just wanted to say that I had a near constant headache, including 2 migraines, until I got to the 5th injection of my loading dose, as well as lots of aches and pains as nerve endings reawakened. It is very common at the beginning of treatment. My folate level was very low and although I was taking 5mg a day alongside the jabs I think it took a while to build up.

Your symptoms may have been a sign of the treatment actually working...

However, I totally understand you not wanting to try again. If you find the sublinguals are not working I think the PA Society have the names of a couple of doctors that treat patients who are allergic - details on their website if you are a member, or you could call them?




I seem to remember you saying that you had headaches at first with your injections.

I haven't heard or read, that those symptoms I had may be a sign of the treatment working? but like most of us we do as the Doc. say's. and he said for me to stop the injections.,and as I did feel rather grotty, I did so.

My symptoms wasn't just a headache, they were also a fever with hot sweats, which lasted all night, dizzyness, and a red rash all over my legs.

I do know that having kidney problems [ which I have ] can cause pins and needles in the arms, legs and feet , and as the b12 society said "symptoms of low b12 can also have the same symptoms as other diseases."

But as I have high blood pressure, which affects the kidneys, which in turn causes anaemia, I probably do have b12 deficiency, even though I was told I was I was within the limit of 226.

According to the GP who looked at my last b/test didn't think I was anaemic, so didn't need iron tablets ? as my haemaglobin [MCH ] was 30.1 the range is 27 to 32 so I assume it's just the b12 I'm lacking. I wont bore you again with the other results, which I already told you before, and I also told them again to

"nostoneunturned" above.

Like I have said before this all new to me, and I thank you all for your info, which I am trying to absorb, I really appreciate it, and at least I can go "armed" with my knowledge when I do go to the hospital. I think I will take my b12 book with me!!!!

I am still waiting for my appointment at Addenbrooks, re my blood pressure and kidney's. I was refered at the beginning of April !! It appears that my referal has got lost in the system, so my surgery is chasing it up.

I'm hoping that I can get some satisfaction from him WHEN I finally get the appointment.

I'm also thinking that these injections I had will be OUT of my system when I go to the hospital, as any further blood test may show a higher b12 level. Any idea how long the b12 stays in the system before the levels drop again ?



You could definitely be reacting to something in the hydroxo solution, I don't know really, but because you had rashes and fever I think your doc probably did the right thing. I have some hydroxo ampoules and they also contain sodium dihydrogen orthophosphate, sodium chloride and water.

I don't know if there has been any research done on people feeling worse when they start treatment. I just know that anecdotally from the PA website lots of people do.

Regarding the B12 in your system, I think what would be really handy is to see what your levels are right now (after 3 injections), so if you then ask for the B12 to be repeated at your hospital appointment you can see if it's dropped back down again, perhaps proof that you are not able to retain it. Just an idea, I'm no expert I'm afraid.

H x


Although if you're now taking the sublinguals then no point in getting retested, might as well just follow nostoneunturned supplement regime and see how you go.


Today i had my 1st ever B12 Injection which hurt for a while (it felt like i had been punched several times on the arm). A Few Hours after, whilst i was just sitting on my sister's sofa at her house just watching tv, i started getting Stomach Cramps, i felt like i was going to pass out & i felt like i was going to throw up, also felt dizzy & lightheaded as if i was stoned. Since about 8pm i have now been suffering from Diarrohea! I am not looking forward to the next injection on Friday at all!


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