Pernicious Anaemia Society
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Different types of B12 - which is best and why?

My endo has written me a private prescription for B12 to inject - I don't have PA as far as I know but am hypothyroid with a variety of digestive problems and find it difficult to tolerate oral supplements. She has prescribed 1mg every other day x 3 doses, so I don't know what I'm supposed to do after that - I think it's just to see how I get on with it, although I don't expect to notice much difference on three doses.

I've rung round the local dispensing chemists and all that they seem to offer is cyanocobalamin. As the prescription for 3 ampoules from the chemist is going to cost more than it would to get cyanocobalamin from the 2 UK internet sites that I know of, I'm not sure what to do. I would rather get it on prescription because at least I can be sure of what I'm getting, but also I thought that hydroxcobabalmin was the preferred type for injection - (and methylcobalamin for oral use) - and no dispensing chemist seems to offer that.

I did find an internet site that offered 1mg ampoules of hydroxocobalamin, but it came from all manner of parts of the world, and without wishing to sound bad, I'm a bit worried about ordering it, let alone injecting it.

Could somebody please tell me what is so bad about cyanocobalamin - apart from the obvious 'cyanide' connotation? If anybody knows of a reputable source of hydroxocobalamin, perhaps they would be kind enough to pm me?

I believe the PA Society has a doctor they recommend, but at the moment I am not well enough to travel long distances to consult anybody. I would be very grateful for any advice. Thank you.

Kanga x

1 Reply

Hi Kanga,

On the PA Society forum you will find which websites people use and find their service is reliable, re buying B12 on the internet. I do not buy on the internet but go abroad often so buy it there at the chemist, Very cheap!!

You know about the cyanide molecul etc , but I'm for convienience pasting a previous reply below to kind of give you my version of what I think the diferences are oin certain B12 preparations. I personally use cyanocobalamin bought abroad (prefer it, it does not sting and seems to me to work much quicker, as on wake me up), then I have once every 2 months hydroxocobalamin, which takes for me longer to "wake me up" and gives me an upset stomach for a bit. Methylcobalamin lozenges did nothing for me..

cyanocobalamin and hydroxocobalamin are forms of B12 that still need to be converted in the body to methyl and adeno B12.

Cyanocobalamin also first needs to have the cyanide molecul taken off so has an extra conversion needed compared to hydroxo cobalamin. Hydroxocobaamin attaches itself to cyanide and is therefore used for smoke inhilation/ fire victims etc.

With a certain eye condition, cyanocobalamin should not be used (Leber's hereditary optic neuropathy). Tabacco ( particularly chewing) can also cause an eye condition that prohibits the use of cyanocobalamin (Tabacco amblyopia, and optic neuropathy).


Cyanocobalamin is the cheapest and most stable form of B12, has a long shelf life, and official maintenance dosis is once a month.

Hydroxocobalamin is a "longer lasting" form of B12 (retained in the body longer) and cost more and has a shorter shelf life plus official maintenance dosis is 2-3 monthly depending in which EU country you live.

( My experience is cyanocobalamin is taken up quicker and does not sting like hydroxocobalamin does,but I need it more often, never tried methylcobalamin injections as I do not want to inject more often).

There are depot preparations of cyanocobalamin that also are suposed to last longer .

Methyl cobalamin is the most natural form of B12 , needs no converting, has the shortest shelf life (will convert back to hydroxocobalamin if not stored right etc), is the most exspensive, maintenance is more regular, often infusion, with then daily/weekly sub cutain top ups (Methylcobalamin not licenced in UK, so you can not get injectable methylcobalamin from a chemist in UK).

I hope this is of use, for compleet explanations one can use pub med site and put all forms of B12 into their search options, or use the WHO website, or the BNF ( registration needed).

All will give technical details that I find difficult to reproduce!

Kind regards,



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