Pernicious Anaemia Society
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B12 infusion or Injection?

Why would people have B12 infusions? Is it more superior than SC or IM injections?

Apart from the fact that the infusion can be prepared with B12 with calcium and magnesium, I don't see any other benefit. I just wondered because injection is so much quicker and cheaper. B12 IV will go straight into the blood system but I'd say that the IM injection starts to work just as quick e.g. within 15 mins.

9 Replies

I have heard that the infusions are good for people who have very low B12 levels or who are feeling very unwell. A lot of people, myself included, do not benefit from injections immediately. It can often take many, many months of regular injections to start to feel normal again. an awful lot of people do not get the correct loading doses and cannot survive on 3 monthly injections. I have been self injecting once a week for the last 3 years, in the first year of diagnosis, I need 2/3 injections per week as my levels were so low and I could not function. We are all different and I think that if you benefit from SC or IM injections in a short amount of time, then you are one of the few lucky ones. Also, there are a lot of people who are refused injections by their GP's as they are not deemed low enough in B12, so they often take matters into their own hands and have an infusion.


Interesting Luna. So you are having to inject weekly even though you have been on it for 3 years. If you don't mind my asking how low were you when you first discovered? I cannot survive with the amount my GP allows me so I am having to inject myself twice a week and I am coming up to nearly a year now since my first result which was just within the lower range. I don't know if it will ever get better. :(


Hi Luna,

Just read your reply re: vit B12 injections. Like you I cannot survive of 1 x 3 monthly injection. My GP states that the results of B12 are OK, although a bit on the low side, and, wait for it........thinks that any more B12 will not make any difference!!! Can you tell me where I can purchase B12 (ampoules)? and, which is the best/cheapest to buy them from? I have looked on "" from Germany.......Regards


Erainy, my B12 levels were around 70, ref range, from memory, was 200-700. Folate was very low but I had to ask for folate to be tested, they don't seem to know/care, that without folate, B12 is not utilised. Ferritin was in the middle of the scale but very often it needs to be on the higher end to make a difference. It took my Dr 4 months of weekly investigations to finally diagnose PA. He sanctioned me having my injection once a week for 3 months after initial loading doses, because I was so low but wouldn't help me self inject as he wasn't comfortable with it. My vet showed me how to self inject in the end. I wasn't prepared to battle with the GP over it as my life was slowly grinding to a halt.

Gillandandy, unfortunately your GP's attitude is very common. Has your folate, ferritin, thyroid etc been tested? As I said above, you need good amounts of folate for your B12 to be effective and do its job. In saying that, some people, no matter how much B12 they get will only absorb a certain amount of it. This is why the active B12 test can be so useful, to see what you are actually using rather than blood volumes of it. I haven't had this done as you need to go without B12 for around 6 weeks beforehand to get an accurate result and I couldn't go without for that long. Sorry if you are already aware of all of this. I buy my B12 in the 2 ml ampoules from as they are a good price and also, the B12 works well for me. I buy my syringes and needles from medisave over here in the UK. Have you looked at the Pernicious Anaemia website? All the information and help, including for self injecting is available on there. I split my ampoules into two injections, 1 ml each time as it is too much for me to inject in one go. I also now inject sub cutaneously as it is less painful but just as effective, but without the bruising Lol. But everyone is different, IM was just too painful for me to do on a bi weekly basis.

Hope that some of this has helped.


Thanks luna. wow, you were quite low then. I was just over 200 and I couldn't get up though. I couldn't go without an injection for 6 weeks, I will be very ill and cannot function due to various symptoms. So bad that GPs don't really know/care about folate and B12 link and it's terrible that you had to ask help from your vet. I was the same though. I had to go into another NHS medical centre so that they could help me learn how to inject. I explained to the receptionist & nurse why I wasn't treated and in the end they accepted me for free when I told them that my gp prevented me from going to other walk-in centres because he would get charged. My only last resort was to seek help from junkies on the street. It's really a lonely world but I've learned my lesson. Doctors, especially GP, aren't there to help you. They are working for pharma industry, to prescribe, to push you with unnecessary drugs to make you even ill, cancer treatment is a good example.


Its very sad. GP's don't take PA seriously and don't realise the impact that it has on your life. My teenage Daughter is only around 230 on the ref range and has very obvious symptoms but as usual, the GP's say that she is "within" range so doesn't need any treatment, despite PA being auto immune and quite possibly hereditary. You are completely correct regarding drugs, I was put onto very strong pain killers for the muscle pain and also steroids before diagnosis, these did me more harm than good. They are only too happy to push drugs rather than a simple, inexpensive vitamin injection.

I hope that you are as well as you can be and continue to stay that way.


Thanks Luna. :)

Last week I skipped one injection to see what happens and I think I took some steps back so I'll have to keep up with it again to build it up. It seems like I can't store B12 in my liver or have nothing stored even though I should have.

My GP is the same. My muscles get very stiff for no reason (not the result of exercise anyway) and pain. I also get nausea too and I know these symptoms goes away when I have an injection but of course my GP don't think it's due to B12 deficiency so he is too happy to prescribe painkillers and anti-nausea tablets when B12 injection is the right thing to have.


from the info i've gathered over the years, you also need large doses of vitamin c to utilize b12 and store it in the liver. also from what my doctor told me, b12 deficiency is usually coupled by deficiency in on or more of the b complex vitamins. folic acid is most common, but the rest are as important. currently waiting for b complex tablets from iherb to arrive.

one question. how does infusion work?


And, with B12, you don't want the whole lot in the blood in one go.

Any B12 in the blood over a certain amount will get eliminated in the urine. So an IV dose will mainly get eliminated. But an IM or SC dose will enter the blood slowly, which means the peak levels will be lower than with IV.

Suppose the inland Revenue decided that any amount of money in your bank account over £5000 would be instantly removed and given to the government.

if you earn £5000 a month then you'd want to get paid monthly, as the amount removed would be fairly small. But if you got paid the whole lot as a lump sum once a year then most of it would be confiscated.


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