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Pernicious Anaemia Society
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I think I'm losing the plot....desperate for some perspective

I have been self injecting b12 since last August.... With very good results. I have never made a full week before symptoms return so have been injecting several times a week. I read a post on the thyroid forum the other day about a correlation between supplementing b12 and folic acid and cancer.

Reading this really freaked me out. I'm normally quite grounded but this information just sent me in a spin. I am now scared to continue supplementing ..... Last injection was Tuesday and today I saw the return of some symptoms....pains in my wrists and hands, tingling and numbness in my fingers, painful feet, very loud tinnitus and very lethargic. I'm so confused. Common sense tells me to continue with the b12 but I'm really scared.

Also, why do I need to inject so often? Literally 5 days without injecting and I feel unwell.

Can someone shed any light on this claim that high supplementing of b12 can cause cancer?

I'm usually very level headed but I really feel like I've dived down a rabbit hole and can't get out!!

Hope someone can help

Thanks in advance

Lu x

13 Replies
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I would like to know where that information posted on the thyroid forum came from . Chapter and verse is needed, with medical proof . I am 100% sure that it is totally unfounded . You can find medical information on the pinned posts that there is no danger in even massive doses of injected B12 . Please calm down and continue to inject . Don't forget to supplement with folic acid in case you are not getting enough in food (green leafy vegs) You need both to get rid of symptoms .

The only evidence I've heard of concerning cancer and B12 is that Pernicious Anaemia patients can have a slightly higher risk than normal ,of getting stomach cancer . It has to do with that condition . But it has NOTHING to do with B12 injections . I want you to know this straightaway . You might be so worried that you are waiting for a reply now in the wee small hours .(3.15!)

Someone more knowledgeable than me will be in touch I'm sure . In the meantime , carry on injecting !

Very best wishes to you .


wedgewood thank you very much for your response... I'm going to inject as soon as I get up. Woke up in so much pain this morning. My folate levels were checked in October and were slightly over range (following taking methylfolate for 2 months). I now take a b complex (quite low doseage) every time I inject.

The initial link on tuk was to a website called forefront health and to a blog within that about low ferritin and hypothyroidism. It was within that blog where mention was near to high b12 supplements and cancer. No reference other than it was a Norwegian study, based on a group of cardiac patients supplementing with b12 and folic acid alongside a test group who did not. Higher percentage of the supplementing group developed cancer with poor prognosis . Sorry I have no links to post. When I get up I will see if I can post links (at the moment I'm using my phone which I'm not sure how to use the cut and paste facility!)

Again, thank you for responding to me in the middle of the night

Lu x


You have had a marvellous and detailed response from deniseinmilden , which I'm sure has put your mind at rest. Just keep persisting . It might take some time before you have result you want . Don't give up . We will always respond when you need some reassurance .


Whoa there! Don't panic!

B12 is used in DNA in every cell in the body as it reproduces by cell division.

(Except red blood cells which are synthesised by bone marrow and don't have a cell nucleus).

If you are B12 DEFICIENT for a long time it is possible to get problems with cell division because there isn't enough B12 to correctly copy the DNA and the cells produced can form with the wrong genetic code and become cancer cells. As these cells with their new wrong code divide, the cancer grows.

If you have plenty of B12, cell division is not limited and can happen at an optimum rate, which is hence why we look and feel so much better, including having healthy skin and hair, when we supplement at a good rate. It also enables our white blood cells to reproduce at the rate required to fight infections.

IF, often due to a long term B12 deficiency, you have cancer cells in your body and you then have optimum levels of B12 these cells can reproduce at their optimum rate, as well as good cells and so any cancer you already have can grow.

So the accepted recommendation is...

If you don't have cancer, supplement as much as required to bring your levels up to eliminate any deficiency within your body (at the very least to a level where you cannot get any further improvement in symptoms) and so reduce your chance of getting cancer. If you do already have cancer get it treated as soon as possible and supplement under the guidance of your oncologist.

If you don't already have cancer, do not worry about your rate of SI. The BCSH guidelines state that you should have every other day injections until all your neurological symptoms are resolved. There are lots of people for whom even this isn't enough and we just have more, to good effect. I use 1.5 mg in 1 ml hydroxocobalamin ampoules daily and there are several people who do 2 jabs a day. I have heard of people who have been on daily jabs for 38 and 45 years to keep well.

If your body needs it, it needs it! A deficiency causes damage.

B12 is also used to recycle homocystenine, a build up of which is linked to aneurysms, strokes and heart attacks. Many of the symptoms we feel are due to nerve damage, including brain damage, caused by a lack of B12 and this can become permanent.

If you are feeling anxious and not as level headed as usual it could well mean that your potassium and magnesium levels are low, and maybe folate too. This happened to me after about 6 months of SI. I suggest you Google them to see if it might be the case for you.

For more information, including sources of supplies you could look up my profile by double clicking on my name and see my post, "My Experiences".

Do your jab - feel better and sort it out when your head is clearer.


deniseinmilden that makes perfect sense.

I take magnesium at bed time every night. As for potassium I do think I have a tendency for this to be low, even before I started with the b12. I had it checked twice last year and both times it was bottom of the range. I started occasionally using lo salt (which contains potassium) and drinking Smart water . Also do try to eat potassium rich foods.

Thanks for your post. Exactly what I need, common sense and straight talking

Lu x


Thank you for your lovely reply. It's good to be able to help.

I use LoSalt a lot and at one time needed well beyond toxic levels every day just to survive. Thankfully I need a lot less again now as I improve.


How do you know if you have any cancer cells? Do they have to do a biopsy?

1 like

Scans, blood tests and biopsies are the usual way cancers are discovered or ruled out, I think.


Hi Lulu_65 I've been "supplementing" every month with B12 and folic acid for 45 years and I'm still "clivealive" at 75.

I think there is a danger of people with P.A. developing stomach cancer but it's only a quite small percentage and it could be more a case that it is the B12 deficiency that is the cause rather than the P.A. itself and as wedgewood says "carry on injecting !"


Hi all

wedgewood , deniseinmilden and clivealive . No causal link has ever been established between supplementing with high doses of B12 and higher rates of cancer and larger tumours but there have been studies that have shown a correlation.

One cause of B12 deficiency - PA - is linked to a process that can lead to stomach cancer, so risk of stomach cancer is slightly higher for people with PA.

My personal theory on the link between being treated for B12 deficiency with injections and higher rates of cancer is that the causal link is likely to be the period of B12 deficiency before treatment started meaning that there was an unidentifed pre-cancer or unidentified cancer and the larger tumours would be explained by the fact that B12s role in reproduction of DNA also means that the cancerous cells replicate a bit better than they otherwise would.

Lulu_65 it is important to understand the difference between a correlation and a causal link. A Correlation just shows that statistically one item that you are measuring varies in the same way as another variable. A causal link means that one variable is affecting another directly.

So, to give an example - if you are taller you will tend to have a larger shoe size - that's a correlation. However, it isn't being tall that causes your feet to be bigger.


wedgewood, deniseinmilden , clivealive and Gambit62

Just want to thank you all for your responses to my panic post. I have been worrying about this since early last week and found myself in the 2am twilight zone stuck between a rock and a hard place. (Thank you wedgewood for your very quick middle of the night response)

I had a b12 injection about 3 hours ago and am starting to feel a bit better already.

Thanks for helping me move on from my .... Forgot the word .... I'll call it hysteria!!

Have a nice day everyone. I'm off to spend the day with my daughter πŸ˜ƒ

Lu xx


Often you will get scare articles like that with false information, its how they get revenue and make a living

quite sad.


These postings make good sense and explain a lot for me too. Hope you get better soon x


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