Increased cancer risk?: I have low... - Pernicious Anaemi...

Pernicious Anaemia Society
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Increased cancer risk?


I have low-normal (215 ng/L) non-anaemic B12 deficiency, with multiple neurological symptoms. When I queried a consultant about having alternate day B12 injections, she said there was an increased cancer risk if I did so. Google says there can be a 15% risk of lung cancer even for non-smokers with too much B12. I am a 78 y/o male non-smoker (never).

Any comment?

37 Replies
clivealiveForum Support

Hi Oundle Rubbish - she should read the BNF Guidelines


I am not medically trained but have been having B12 injections every month for over 47 years and I'm still "clivealive" aged 78

I wish you well and bid you goodnight

in reply to clivealive

Thanks clivealive.

in reply to clivealive

That's good to know Clivealive, which injection you have been taking? Hydroxycobalamine or cyenacobalamine? Thanks in advance.

clivealiveForum Support
in reply to nkindia

I am on cyanocobamalin (now every three weeks) as this was what I was started on back in May 1972

We must both have been born in 1941?

My dr did not want to give alternate day injections either. But did not say why. Maybe this is why. A lot of people do alternate day injections without consequences. Would like to learn more. Maybe someone has someone can explain why this comes up on the internet. I now do weekly injections

Dr's with minimal knowledge can get muddled about this.

What actually causes the cancer is high levels of homocysteine as a result of prolonged B12 deficiency.

Where they get muddled is that if you have plenty of B12 and supporting supplements then all cells are able to replicate optimally, allowing growth and repair of tissues.

Unfortunately if you have been B12 deficient for a while, allowing your homocysteine levels to be high enough to cause some cells to become cancerous, any cancerous cells in your body can replicate optimally as well as your good ones.

If you don't cancerous cells when you have B12 injections you will be fine and you will have less chance of getting cancer once you start them than without.

This is why you should have enough B12 to keep your symptoms away as only symptoms can show if your cells are getting enough B12. If your blood has high B12 once you have had injections it shows that the cellular intake mechanism isn't working properly and so some of the B12 is staying in your blood. This indicates that you need more B12 to get at least some into your cells.

Some chemo works by locking up the vitamins and minerals in your body and literally starving all your cells. As the cancer cells have the greatest demand for nutrients because they are (trying to) rapidly subdivide, they are the first to "starve" and die off, hence why any tumours then shrink. But this is also why B12 and folate deficiencies show similar symptoms to having chemo.

If you are 78 you should try to get enough B12 and supporting supplements to banish all your symptoms so you can have plenty of healthy years to come! "Old" age should not be used as an excuse for poor health, especially if it is simply due to decreasing vitamin and mineral absorbtion.

Go get your regular jabs and get well!

Thanks for a detailed explanation. Much appreciated.

Hi Denise, so good to read your reply and explanation. So basically we need to check our homocysteine levels? I do have an annual homocysteine test. I wonder if the info re B12 is coming from researcher Dr Kara Fitzgerald who I heard state that (I think Cancer Research) has not found 1 case of cancer where the patient did not have high levels of serum B12. This was worrying to me. She stated that she now for that reason recommends her patients getting B12 from food sources only. eek. I also read somewhere that B12 should not be found circulating in the blood stream at high levels and any supplement should therefore be taken with food. Kind of doesn't help with folks who have injections or take sublinguals.

For me the bottom line is simple - without daily injections I won't survive long enough to have the opportunity to get cancer!!

There are people who have been on daily jabs for decades so it's obviously not directly linked and I'd be inclined to carefully question anyone who claimed it was! At the very least I'd wonder if it was the chicken or the egg?

Well said x

in reply to LynneG

LynneG. I think it's really important to distinguish between high levels of B12 due to an underlying medical condition (cancer being one) and high levels of B12 due to vitamin B12 injections.

If this doctor advises all her patients to get vitamin B12 from food only, then she is consigning her patients with vitamin B12 deficiency (from PA or any other cause) to a long and slow (but inevitable) death!

This is quite shocking...and perpetuating these myths is another reason why so many people are unable to get adequate treatment for PA (and B12 deficiency from other causes).

Sorry...but...shame on her! Shocking!

in reply to Foggyme

Hi, maybe I panicked and misenterpreted her, maybe she qualiied her statement dependant on patient status. I don't remember her doing so. I just remember feeling quite shocked. I will see if I can find further info on her website to post. I believe her info re high B12 correlation was from Cancer Research.

in reply to Foggyme

It was definitely in interview months ago in which she was dicussing her massive global research programme and so her concern re correlation was mentioned in passing. This article post is from her website - gives a different perspective when fully discussed but the reasoning and concern is still the same.

in reply to LynneG

LynneG. Swift glance and this has nothing at all to do with cancer risk, B12 deficiency, and withholding B12 because it’s associated with an increased cancer risk.

Appears to be about over-methylation (in the broadest sense, over-supplementing with folate - which we regularly flag here as a problem (to do with potential neurotoxicity and long term neurological damage).

Sorry but I can't see any correlation or connection with what you refer to as the 'reasoning and concern' about high vitamin B12 levels from a potential cause of cancer!

As I said above...👍

in reply to Foggyme

Right sorry, hypermethylation would be too much methylation which can be caused by too much methyl supplementation however raised.

'Hypermethylation of the promoter region of genes is associated with an increasing number of disease states, including allergy (Martino et al., 2015), autoimmunity (Nakano et al, 2013), Down syndrome (Jin et al., 2013) and cancer (Varley et al., 2013). Particularly breast cancer'

So I have misinterpreted this ?

I had found this on her website following listening to her interview in which she referred to working with Cancer organisation stats and not seeing a case of cancer without high serum B12 and her concern with over methylation. So much so that she has stopped or become v cautious about prescribing B12.

I replyed to the post and this link was to explain my comment and concern. I thought it maybe where Oundle's doctor had information from but there are obviously other studies out there judging by other comments. I am now more confused

in reply to LynneG

LynneG. In short, this article is to do with the methylation process related to folate (not vitamin B12).

I think you may have conflated (or confused) this with her apparent comment about 'not seeing a case of cancer without high serum B12'...and as I said above, there is a distinct difference between high levels of B12 due to an underlying health condition (I.e. cancer), and high levels of B12 due to injection. In neither case does the raised B12 cause cancer (in the former the underlying medical condition is the causative agent: the raised B12 level is a byproduct of the illness - cancer - rather than the agent that caused the cancer. In the latter...well...B12 injections in themselves do not cause cancer.

To date, there is no proven causal link between high B12 levels from injections and other replies here also indicate.

Suffice to say that withholding B12 injections is not an option for those who are B12 leads to death.

There are circumstances where B12 has to be given with caution...and one of them is in the presence of cancer (not that the cancer is caused by B12, I hasten to add). This is because B12 increases cell replication...and obviously an increased production of cancer cells is not desirable. However, neither is neurological decline and death from lack of treatment for a B12 deficiency. So, in cases where there is an underlying cancer (or indeed if cancer develops at a later date - and again, I'm not saying cancer because of treatment with vitamin B12)...B12 therapy still MUST continue. And the answer here is to give enough B12 to manage symptoms (keep them entirely at bay - prevent neurological decline and nerve damage)...and to give no more B12 than is necessary to do that. (Just wonder if this is one factor that’s causing you to feel confused about the whole caboodle 😉...?)

And indeed, as Gambit says below...being B12 deficient itself can cause cancer...

In the above senses it might be simpler to think about the consequences of NOT treating B12 deficiency (rather than the complex process of methylation/hyermethylation - as described in the extract in relation to the methylation/hypermethylation of folate...if you get what I mean).

Sorry, but I haven't the time right now to engage in further discussion about this.

Suffice to say...withholding B12 treatment on the basis that high serum B12 levels are found in those with cancer is...well...a deadly mistake for those with B12 deficiency.

in reply to Foggyme

Thank you for your time Foggyme and your explanation :)


I think your consultant should weigh up the risks of not giving adequate B12 treatment which includes permanent neurological damage including spinal damage.

A lot of people on this forum have a diagnosis of PA (Pernicious Anaemia). Pernicious means deadly so I assume that not treating PA adequately carries severe risks.

You can have PA (Pernicious Anaemia) without having anaemia.

Were you ever tested for PA?

PA tests

Intrinsic Factor Antibody (IFA) test

Parietal Cell Antibody (PCA) test

PCA is not recommended as a diagnostic test for PA in UK.

Both these tests can be unreliable.

It is still possible to have PA with a negative result in IFA or PCA test.

About 50% of people with PA test negative on IFA test.

About 10% of people with PA test negative on PCA test.

I don't have a confirmed PA diagnosis although I had many typical b12 deficiency symptoms for years including many neurological symptoms ( I still have some symptoms).

I think untreated or under treated B12 deficiency from whatever cause carries risks. At one point before I got treatment, I felt I was dying slowly as my body continued to deteriorate.

Neurological Consequences of B12 Deficiency

PAS news item


PAS article about SACD, sub acute combined degeneration of the spinal cord, access to PAS members only.

pernicious-anaemia-society.... See Page 2 of articles.

Blog post from Martyn Hooper's blog, mentions SACD

PAS (Pernicious Anaemia Society)

Based in Wales, UK.


PAS tel no +44 (0)1656 769717 answerphone

PAS support groups in UK


Blog post about how PAS can support PAS members seeking PA diagnosis

You mentioned in a previous thread that you were having support in trying to get adequate treatment. I hope you are still getting support.

If you join PAS, you may be able to get support from them.

Unhappy with Treatment (UK info)?

Letters to GPs about B12 deficiency

CAB NHS Complaints

HDA patient care trust

UK charity that offers free second opinions on medical diagnoses and medical treatment.

BSH Cobalamin and Folate Guidelines (UK document)

Guidelines above mention many patients with B12 deficiency do not have anaemia.

Flowchart from BSH Cobalamin and Folate Guidelines

Flowchart outlines process for diagnosing PA and Antibody Negative PA in UK

"Treatment with high dose vitamin B12 been shown to be safe for more than 50 years"

"Misconceptions about a B12 deficiency"

"Google says there can be a 15% risk of lung cancer even for non-smokers with too much B12."

Even if a study showed an increased risk for patients on high levels of B12; I'd want to know more about the study before I got worried. For example I'd want to know if there were other risk factors in the lives of the people in the study.

I am not medically trained.

in reply to Sleepybunny

Many thanks for your full answer.


Studies show correlations between B12 injections and cancer but no causal link has ever been established.

The correlation may well reflect the fact that being B12 deficient can cause cancer so people who are being treated for absorption problems may have developed cancer/precancerous conditions whilst B12 deficient. Meaning that the causal link could be the preceding period of B12 deficiency rather than the treatment for it.

in reply to Gambit62

Many thanks.

I think your doctor js getting cause and effect the wrong way round.

High levels of B12 are associated with some cancers (especially liver cancer. But the cancer causes the high B12, not the other way round.

in reply to fbirder

Many thanks.

in reply to fbirder

Do you know how that happens fbirder, any links?

in reply to fbirder

Thanks fbirder

in reply to fbirder

Thanks fbirder - totally makes sense that correlation is being misread. So reassuring, thank you

CherylclaireForum Support

I have been self-injecting for over 2 years on an alternate day regime, after failing to get any better at any other frequency (and getting a lot worse on some). Only this has worked for me, but very slowly and not without setbacks.

I have needed to also pay close attention to folate and ferritin levels- as they often dropped to low-range levels at which point symptoms got worse: gums bleeding, hair falling out, fingernails splitting vertically - signs that would make you think of malnutrition. This despite frequent B12 injections and a good multivitamin and mineral tablet daily. So have had to supplement with ferritin/folate at times on top of this for short periods to boost levels again.

Now all my bloods are looking good, better than they have for at least 5 years (since first becoming ill) - and I have reduced injections to about 2 a week, depending on symptoms and energy levels etc. My GP checks levels regularly to ensure I'm still okay, but never checks my B12 now as there really is no point. She checked it twice after having NHS administered injections in 2016, and both times it was over measurable levels (over 2000ng/L) which is where it has probably stayed since. My homocysteine was tested and found to be normal (7.2 pmol/L) in 2017 .

Regarding B12 injection frequency: I don't believe there was any other option for me, as I would have continued deteriorating in B12, folate and ferritin. I'm not worried about cancer risks, I'm focussing on a return to my former healthy self. It's working for me.

I am seeing a Metabolics consultant who said that if there was a problem with cellular uptake found in DNA, she would advise that B12 be administered twice a week. Which means that the NHS don't see this as a dangerous level -or they wouldn't be giving this feedback to GPs.

deniseinmilden, always worth a read, has made some sound points above that I hadn't considered before. Take your time to read through Sleepybunny 's links, too: reliable research information that will hopefully put your mind at rest.

Take good care.

in reply to Cherylclaire

A very interesting and thought provoking response. Do you get your injections by the NHS, or do you buy from abroad? Thanks

CherylclaireForum Support
in reply to Oundle

Because I had decided to self-inject as the NHS was unable to stabilise my condition on any regime they offered me (it kept changing), I had to buy my own.

I made the mistake of seeing another GP while my usual GP was away on holiday. Because he was completely freaked out about my frequency, he discussed my case at a practice meeting -without first discussing it either with me or my usual GP, who was still on holiday.

My NHS injections were stopped and he sent me a letter requesting that I stop self-injecting completely and rely solely on the NHS regime of 1 injection every 2 months.

One that had previously not been effective.

That did not feel like a choice.

I still self-inject, at a frequency that is making me improve slowly. Any other action on my part would be risking deterioration which, to my mind, would be a very foolish step backward. It has now been 5 years since I first went to the practice with inexplicable fatigue being one of my main concerns.

Luckily, we are not all the same. Neither, it seems, are our GPs.

Thank you!! ☺️

B12 (and folate) are actually used during chemotherapy for lung cancer!

To reduce side effects while having pemetrexed and cisplatin you need to:

take folic acid tablets – starting 5 days before you begin treatment, continuing throughout treatment, and for 3 weeks after treatment ends

have vitamin B12 injections – 1 injection in the week before you start treatment and then 1 before every 3rd treatment cycle (every 9 weeks)

This is a recent paper which makes strong claims about B12 association but I am not impressed by some of the wording.

Is high vitamin B12 status a cause of lung cancer?

This paper is a little bit more interesting - especially as it very definitely looked byond serum B12.

Vitamin B12 and its binding proteins in patients with non-small cell lung cancer referred to fast-track diagnostic work-up for lung cancer

We thereby confirm the association between non-small cell lung cancer and high cobalamin levels and found that haptocorrin was the major underlying factor causing high cobalamin levels.

CherylclaireForum Support

To add to confusion here, regarding cancer risks, read "Discomfort in toes and feet" posted (below) by shaws regarding her mother's injections being stopped despite having PA.

Re helvella 's link to paper on haptocorrin and cancer:

I once had problems with salivary glands and ducts: infected and strictures respectively, leading to swelling of parotid glands. An ENT consultant agreed with me that this could well have affected my ability to absorb B12 from food (extrinsic factor) - as haptocorrin from saliva is employed in order to protect B12 from being destroyed by stomach acid.

Perhaps the opposite is happening here: too much B12, because of overproduction of haptocorrin ? What the cause of this could be is beyond me: perhaps cancer of parotid gland (?)

I'm inclined to agree with deniseinmilden : B12 has allowed me the time to worry about any possible long-term side effects. So I'm not going to - not when evidence seems flimsy/ misguided.

PS: I smoked like a wet bonfire for 35 years- only gave up completely when I became ill 5 years ago.

Perhaps haptocorrin production increases if the person is B12 deficient?

Quite a lot of biological processes adjust depending on circumstances. Could this be one?

Of course, B12 deficiency might not mean low serum B12.

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