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Pernicious Anaemia Society
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Cyanocobalamin-- migraines? toxicity?

Anyone know if there more of a prevalence of chronic frequent (ex 2-3 times per week) migraines with cyanocobalamin injections versus other forms of cobalamin? My migraines began 6 years ago at age 40 when diagnosed with PN.

I have had 1 month cyano injections for 6 years, take no multi or other tabs. I found out recently my levels are still kind of borderline low for someone with monthly injections (300). I still have some symptoms such as memory, fatigue, palps, and have tingeling & numbness in hands and feet that comes and goes. Homocysteine level was mid range and normal. Folate checked and normal. Ferritin normal but on low side around 25. The doctor did not do an active b12 test, just serum.

What is the concensus on toxicity of the small dose of cyanide? Most of what I read online indicated the small amount should not be an issue, but I also read the contrary. Is the methycobalamin injection actually better? Anyone know and have solid data/research to support their information?

26 Replies

Just for clarification - when you say you have PN do you mean PA (Pernicious Anaemia)?


Yes, sorry pernicious anemia---antibody to intrinsic factor was found


Thanks for the clarification. You can edit your posts if you realise you have made a mistake.


Its all a matter of trail and error what kind of cobalamin suits you personally best.

I inject cyanocobalamin IM once ever 2 weeks. For toxicity perhaps have a look at this topic (although most of the links are now broken, still enough info) see:



7.2.5 Acceptable Daily Intake (ADI) and Other Guideline


The Food and Agriculture Organization and World

Health Organization have recommended an ADI of O.O5 mg

cyanide/kg. The life-time Acceptable Daily Intake for

an adult (Drinking Water standard) is 1.5 mg/day

(equivalent to O.O2 mg/kg/day), based on a 7O kg adult

(EPA, l986).



I hope this helps,

Kind regards,



Thank you Marre. The other person who told me cyano was not good is affiliated with another b12 site. They told me cyano is no longer allowed/used in the UK due to the toxicity and also that it does not work in 2/3 people with PA? Have you heard this news?


Rubbish as far as I am concerned. Lets face it, half the world uses cyanocobalamin (most mediteranean countries, USA, South America, Canada) and those countries, specially US and Canada would not use an out of date or secondary product I think. They have good research centres, money for research etc, all just very unlikely to me. Anyway I use both, as in get prescribed hydroxocobalamin once ever 2 months and add self bought cyano. I prefer the cyano as it gives me far more of an instant lift, but I know from trying with and without that hydroxocobalamin keeps my serum levels higher, but gives me an upset bowel for a week or so. It feels to me that the hydroxo takes over a week to "work", whilst cyano seems to "work" for me after a day or so. But it could be because the hydroxo is trying to clear out all the cyanide I inject and will have in my body because I smoke. Perhaps the pharma industry makes more money out of hydroxocobalamin? I do not know, but know I personally prefer cyanocobalamin, never tried injecting methylcobalamin as I do not wish to inject more often than I do now. I know others in US that tried hydroxocobalamin, difficult to get and expensive, but found no benefit, some do prefer methylcobalamin though. Its all very personal I think.


Hi Marre-- Are you in the UK or US? I am curious why you don't just use the cyano injections more frequently and exclusively if you like that formula better? Why use both forms? What would be the benefit? Thank you in advance for your reply.


I second Marre's "rubbish". I'm in the USA on weekly cyano-B12 and find it works fine. I still have issues due to stress, gluten, dairy but when I get my injection (and folic acid) I'm good.

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It can be "rubbish" for some and not for others. This is the big mystery that is B12. If you test positive for MTHFR cyanocobalamin is useless or minimally effective as it does not convert to methylcobalamin in the body. Blood serum can be high but it is not used. That being said, if a person has one copy of the gene (from only one parent), the enzyme needed to convert is reduced by 30%. But if there are two copies, the enzyme is reduced by 70%, making it impossible to sufficiently use cyanocobalamin. Whilst MTHFR refers to the methylation of folate, it applies to B12 and utilization of all B vitamins which need to be in balance.

A tricky one to unpack.

A point to ponder - because MTHFR sufferers also don't detox efficiently, could the cyanide build up over time to then become an issue with migraines? Just a thought.

Cheers everyone.


Hi Fudgewobble,

Yes, I am a heterozygote for the MTHFR gene. I was told my homocysteine level should not be an issue with just one gene. Thank you for the information. That makes sense and I probably do have trouble with other B vitamins. I had my first endoscopy this past week and the gastroenterologist was surprised as he did not find stomach atrophy just some mild inflammation. I have an apt scheduled to discuss more details and am confused as he stated in his letter that these results were not at all typical of autoimmune pernicious anemia. I guess he expected to see atrophy. However, I am just 46 so maybe that would develop down the road. When I was diagnosed by my internal medicine doctor I had a B12 level of 85, many symptoms and tested positive for the anti-intrinsic factor antibody. My levels maintain at 300-500 with frequent cyano shots of every 3 weeks. If I go longer they fall. My diet is very good. I had thought the antibody to intrinsic factor plus low B12 was enough to diagnose the disease.



Although heterozygous is better than homozygous for sure, it seems to depend on whether there are other methyl gene "mutations" happening. On the MTHFR forums, many people have just as many problems as the homozygous even though the doctors have said the same as yours.

My faith in the established medical system has slowly been eroded over the years and I agree with others like Poppet11 that doctors have lost the art of observational medicine.

But we all are on our own journey of good and bad and need to do what feels right. No one can dictate to another, just make suggestions and give support.

Good luck with your next stage.



I am in UK and get prescribed hydroxo, once every 2 months, I buy my own cyano. Have done a year on cyano only but my serum levels did rather drop, I've also tried hydroxo only, plus knew my old GP was retiring so feel its best to make sure I keep on my notes that I am on B12 treatment for life. What worries me when I'm to old and feeble to sort my self out, I need to make sure I will always get something from my GP.


There was a post on the site a couple of months ago by someone who was in the UK and was being treated with cyanocobalamin so it is obviously used in the UK ...


The British National Formulary states:


The BP directs that when vitamin B12 injection is prescribed or demanded hydroxocobalamin injection shall be dispensed or supplied

Therefore I cannot see cyanocobalamin being used for injection by any NHS or other medical establishment. Of course, that does not rule out the odd medic or some sort using it out of ignorance or for some other reason.



Yes the Pharma industry dictates, and yes there are more people in UK on cyano prescribed by their NHS GPs.


As long as the NHS GP doesn't use the 3 month cycle (hydroxo-B12) when prescribing the cyano-B12.


As I read the statement, even if a doctor prescribed cyano-, the pharmacy would have to dispense hydroxo-.

So I do wonder if anyone in the UK is getting cyano- prescribed and dispensed within the UK - other than a few dozy places/people who might not have noticed?


I recall several cases on the old PAS forum of cyano being prescribed and dispensed in the UK so it does happen, purely through ignorance I think. In at least one of those cases the standard hydroxo 3 monthly protocol was still used. Not surprisingly, the patient wasn't doing too well.


Re:"As long as the NHS GP doesn't use the 3 month cycle (hydroxo-B12) when prescribing the cyano-B12" Yes and that has happened. My Dad included (not in UK).

Rod, on the old forum a few people have been prescribed cyano in UK, I do not know if that has now changed for them. Marre.


The migraines could possibly be down to your body getting really low in B6. I found that when i started treating myself at levels I need - admittedly with hydroxocobalamin rather than cyano- my migraines seemed to get a lot worse. Thought it might be down to needing more B9 and body converting B6 to B9 so tried taking small amounts of B6 as well and that seems to have done the trick.

Caveat on B6 though as taken at high doses for long periods it can cause neuro-damage - usually it goes away when supplementation stops but have been some cases where it hasn't - only happens with artificial forms of B6 - no documented cases with B6 from food. Upperlimit in US is 100mg. UK is much lower at 10mg - not exactly clear why there is such a difference - think most of europe is somewhere in between.

As Marre says form of B12 that works seems to vary from person to person - I find hydroxo works best for my neuropsychological symptoms and methyl- seems to work best for more obviously neurological so use a mix of two.


Gambit62 thank you for your information. I am wondering if taking a standard whole food based multivitamin that includes b vitamins (ex fairly low level as would be 100% RDA value) would help keep other b vitamins in balance? Or does one need a separate bcomplex that contains high doses of b complex synthetic vitamins? Hydroxo injections are not available in the US I believe and Methyl injections are also much harder to find.


Not really an expert by any chalk - just enough to guess and try.

I think a good B-complex supplement would probably be better than a broad spectrum ... I'm also not aware of how the amounts I was talking about relate to RDA - would imagine that they are actually a lot higher.

Getting hold of injections in the UK is, in theory, a challenge - regime here is pretty minimal.

I get most of my Bb12 in other forms - nasal spray seems to suit me best - as long as it isn't in an injectible form then it isn't regulated here. Not sure that it is the same in the US but hopefully there will be others who can advise on that. You can get ampoules for injection on-line (but you'd need to use a reputable supplier). I don't know what regs about import for personal use would be in the US .. and as I say not sure what the position is with other formats - sublingual tabs, sprays, skin patches ... as I'm not sure to what extent the FDA regulates them in the US.


The letter - N. Nutt, 24th Sept - and more responses to BMJ Hunt article on B12 def. might help:



Anecdotally, I've been having increased headaches and visual problems ever since I starting taking cyanocobalamin 7 months ago in both tablet and injection form. Recently went off cyano to try hydroxo and although I can't say conclusively yet, it does seem like my headaches and visual problems are improving. My theory has been that my decreased visual acuity was causing strain that led to the headaches.

I know that men can apparently get Leber's Disease, which can cause visual problems and is exacerbated by cyanide. Supposed to be rare, though, but they warn you about it on any cyanocobalamin drug info sheet.

I too have read mixed reports about the toxicity of the cyanide in cyanocobalamin. Most sources claim that the cyanide by-product is a low enough amount that it is usually safely excreted from the body. But knowing that cyanide can definitely poison someone, I'm still not completely sure I trust it.


B12 injections can give you a headache, and flushed feverish feeling, but it should not last and ideally get less once your stores are replenished.

Some info in here, see side effects:



I take cyano-B12 1mL per week of 1000mcg/mL in two doses of 0.5 ml (Wed and Sun evenings). If I get a headache after a jab, it was because I was too low before the jab. The cyanide is not the issue. I self inject my jab in the evening to sleep the headache off.

It is the B12 deficiency (from stress, pollution, etc) causing toxins to build up and when you get the injection, there is a flood of metabolic byproducts into the blood stream. It takes a while for the liver and kidneys to clean these toxins out. You get the headache until your blood is back to normal.

For me, this is one of the indications that I need more B12. I'm stuck at a prescription of 1 mL per week so I supplement with methyl-B12 sublinguals.


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