A common question among people with vitamin B12 deficiency is whether there is a difference between cyanocobalamin and hydroxocobalamin in the treatment of B12 deficiency.
A 2024 article in the journal Nutrients addresses that question. The best I can make of the results of the study is that the answer to the question is "not much", though my understanding of the article is poor. Others on this forum might get more out of the article.
Well if P.A./ B12 d patients who have Leber’s Disease are treated with Cynocobalamin injections , their optic nerve can be seriously damaged and blindness can be caused.
Cynocobalamin was used by the NHS here in UK, until Hydroxocobalamin came along . Cynocobalamin was dropped then because Hydroxocobalamin was reputed to stay in the system longer ,so they could prescribe it less frequently. ….
Thanks for that . It’s important for us to try to get our heads around B12d mysteries , because our GPs , here in the U.K.at least , certainly are not bothered. .
I have tried Cynocobalamin and it certainly worked well for me , but I cling to Hydroxocobalamin because we have been led to believe that it is superior , and one likes to err on the side of caution. where one’s health is concerned. And we are in poorly researched territory where B12 deficiency is concerned. We do live with a certain amount of fear when the ones of us who have had terrible battles with GPs etc in getting a diagnosis and any sort of treatment,look back and remember that awful time.
Battles are ongoing still . .
Question more than answer.
Hydroxocobalamin is used in cyanide poisoning (smoke inhalation) because it binds to the cyanide.
Cyanocobalamin is already bound so would be expected to have no such function.
Rather than effects on absorption by cells, etc., could there be an important difference regarding acting as a cleaning-up agent? That is, maybe some toxins are bound by hydroxocobalamin and removed from our systems. This would probably require an excess of hydroxocobalamin in order to be a significant factor. Such as would probably occur shortly after an injection or, in those who can absorb it, from high dose oral forms.
No amount of research on its action as a vitamin would be likely to uncover this sort of action.
The article states that hydroxocobalamin is more rapidly absorbed in the first few days, (demonstrated by a reduction in homocysteine) but that over the longer term there is not so much difference in its metabolic effect to cyanocobalamin. Maybe the preference of some for hydroxocobalamin is influenced by the perception of a greater initial effect. I have used both forms and after a couple of weeks I can’t say if I noticed a difference.
From a patient perspective and regarding medics who are obsessed with testing after injections to monitor response, I wonder if using more readily retained hydroxocobalamin works against us. Or at least some of us, as after initial cellular uptake the ejected portion simply circulates in the blood showing high levels of inactive b12 attached to both transcobalamin and haptocorrin.
An interesting read. I’m gradually learning the pathways that lead to excess unmetabolised homocysteine and mma. In the hope that one day I can explain ( in under 10 minutes 😄) to my gp why impaired methylation and absorption of b12 are as relevant as an outright deficiency.
Vitamin B12 sublingual hydroxocobalamin
Methylcobalamin vs Hydroxocobalamin 
Cyanocobalamin Clearance 
Methylcobalamin vs Hydroxocobalamin
