B12 Overdose Research

by Chris

Hi Kerri,

I would like to mention that I have found your site extremely helpful.

I would like to bring your attention to this forum thread where the author is compiling a lot of data from research materials to see if there is any risk of an overdose of B12:


After you review the data with an open mind, would you like to consider suggesting a daily or weekly limit of 500 to 1000 mcg of Methylcobalamin tablets for those who are deficient?

Best regards,


P.S. I didn't find any form-field to submit my email address without publishing it publicly in the comment itself.

P.P.S. I found it only after hitting the submission button and editing the text. An early-heads up note on the comment letting users know that the email box will be visible later would help prevent this confusion to others.

Comments for B12 Overdose Research

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Not sure what your point is..
by: Kerri Knox, RN- The Immune Queen!

Hi Chris,

By the way, thanks for the PS and the PPS, but the way that I do it gets the MOST amount of people to actually leave their email address. I can't change the way the email address is put in- and BELIEVE me, I've tried.

I also have people put it 'publicly' so as to overcome this problem. Then I strip it out and put in their email address in the response area as you did yourself. It never gets published 'publicly' because I personally moderate every single thing that is put on this site before it's ever published.

So, I read the forum and, for one, I'm not sure what your point is. Are you saying that I should not be recommending more than 1000 mcg of B12 per day? On that forum, there are hundreds of posts that are not interesting reading that I'm not going to wade through to see what your point is, so if you have any specific RESEARCH studies to point me to to show your point, I'll be happy to look at them- but I don't read forum posts that end up pointing to other forum posts and blogs for reference. I read RESEARCH studies.

Another thing is that I don't recommend ANYTHING to ANYONE. I provide information and it's up to the person to make their own decision as to what to do.

Next, why would YOU recommend the dosage that you are? I have research to back up everything that I've said. If you are trying to tell me that B12 is 'bad' in higher dosages, what is your research that states that it's safe at the dosages that YOU are suggesting I recommend to people??

Next, if you are suggesting that high dosages of B12 is 'bad', have you separated out the research for the different kinds of B12?? All b12 is not made equal. A couple of the posts showed studies pointing to high b12 and FOLATE as being a problem. We know that taking synthetic folate is a problem, so are you sure that the problem wasn't the folate?

Next, there were a couple of posts pointing to the fact that people with RA and some other illnesses have high levels of B12- with the implication that the high B12 blood levels may be the cause of their illness. However, this is a PARADOXICAL problem that TAKING B12 actually will LOWER this high level because these people are actually too LOW and can't convert the B12.

Next, many of the problems that people reported on that forum were after they got an injection. As a nurse, I've seen LOTS of injections go wrong and that's why I don't recommend B12 injections. See my page on B12 Shot Problems.

So, again, if you have STUDIES that contradict the studies that I've read, please show them to me. I will not read a hundred uneducated forum posts to find out your point...

by: Chris

Hi, thanks for the quick reply.

(1) Regarding the email, just leaving a note that an email field is coming on the next page will help solve the confusion. And rather than decrease your subscription rates, it will improve them since many people avoid posting email addresses in their public comments. And your note actually tells us that an email address is needed to receive a reply, with no note with an explanation where to put it.

(2) I have not looked at any studies and I do not know what should be the overdose limit of B12 intake, if any. I was simply bringing to your attention a thread where the original author posts links to such research sites. I thought you may find it useful for your continued research purposes on B12. Though I don't know if he has linked to any studies or merely opinions of other websites.

The author, Korn, has posted a summary in his post #113:


Here are some of HIS views, not mine, which had got me worried about overdosing on B12 when consuming at greater than 500 mcg per day:

a) Cases of increased cancer production in animals receiving high levels of B12 have been published: http://tuberose.com/Vitamins.html

Note: Portion from that page, can be found by finding the term "Cancer" on that page:

"The routine use of vitamin B12 is not advised. Cases of increased cancer production in animals receiving high levels of B12 have been published. A group of French investigators reported a series of cases suggesting that B12 may stimulate multiplication of cancer cells and aggravate the disease."

b) After all, B12 is about growth and cell division, among other things; it is necessary for the rapid synthesis of DNA during cell division. Cancer = abnormal and uncontrolled cell division. Do I know if too much B12 can cause cancer? No. Would I be surprised if it will be proven in the future? Not at all.

Currently I have B12 and D deficiencies. I will make a new post about it soon.



by: Kerri Knox, RN- The Immune Queen!

Thanks Chris,

I'll take a look, however most of those studies are done on Cyanocobalamin which I don't discuss, write about, use or sell. Methylcobalin is an entirely different animal and actually detoxifies many many substances that ARE carcinogenic such as: heavy metals, glutamates (aspartame,MSG and other artificial sweeteners and flavorings) and mycotoxins. Cyanocobalamin (and the other forms of B12) do not have this action. Also the 'methyl' part of the 'Methycobalamin' may actually decrease cancers since a genetic inability to 'Methylate', a specific method of detoxification, is responsible for a certain percentage of cancers- particularly breast cancer.

Methylcobalmin has also been suggested as an effective TREATMENT for cancer in several animal studies.

B12 has also been given as a long term solution for pernicious anemia for over 50 years now with no increase in cancers or chronic problems for these people, so we've had 2 generations of people on B12 long term for most of their lives with no problems.

Also, if Grandma has dementia are you really going to CARE if she has a tiny increase in risk for cancer if she can remember her own name and eat food by herself in a year if if was likely that she wasn't going to be able to before?

Same thing with Chronic Fatigue syndrome, Fibromyalgia, etc. Most people are going to accept an INFINTESIMAL risk (if their even is one- which I doubt) if they are able to get out of bed and play with their kids at the park again.

All B12 is not B12. And again, I don't recommend that people take B12 at all unless they need it.

Since you have both B12 and Vitamin D deficiency, you may want to consider that you have Gluten Sensitivity. Also, if you are experiencing severe fatigue from your B12 deficiency, don't be surprised if you don't feel better on your chosen dose. You may need up to 20 MILLIGRAMS (20,000 micrograms) per day for a while to feel better.

So, when and if you don't feel better taking your chosen dose, you may change your mind about higher doses of B12.

Thanks for the info, if you have any further research on any dangers of specifically Methylcobalamin B12, which is the only B12 that I'm interested in, the only kind I use and the only kind that I sell, I'd be happy to hear it...

Kerri Knox RN Immune Health Queen

Kerri Knox, RN- The Immune System Queen
Functional Medicine Practitioner
Immune System
Side Effects

Links to actual research studies on Methylcobalim and Cancer
by: Kerri Knox, RN- The Immune Queen!

So, here are some links to actual research studies suggesting Methylcobalamin as a possible TREATMENT for cancer. Methylcobalamin is NOT the same as 'Vitamin B12' which is nearly always cyanocobalamin unless it specifically states methylcobalamin. Studies that understand the difference will specifically use methycobalamin:

Cobalamin Compositions for the Treatment of Cancer- I particularly like seeing patents to show the effectiveness of nutrients because they MUST encompass all of their knowledge base. If the author leaves something out then they risk not getting their patent approved.

Effects of methylcobalamin on the proliferation of androgen-sensitive or estrogen-sensitive malignant cells in culture and in vivo

Methylcobalamin decreases mRNA levels of androgen-induced growth factor in androgen-dependent Shionogi carcinoma 115 cells.

Methylcobalamin inhibits fibroblast growth factor-8 stimulated proliferation and induces apoptosis in Shionogi carcinoma cells.

Cytotoxic activity of cobalamin in cultured malignant and nonmalignant cells.

Influence of cobalamin on the survival of mice bearing ascites tumor.(Leukemia)

Experimental study of antitumor effect of methyl-B12.

The modulation of murine immune responses by methyl-B12.

Effects of methyl-B12 on the in vitro immune functions of human T lymphocytes.

These last two I find particularly interesting in light of your statement that B12 encourages cell growth which you consider 'bad' in terms of cancer. This shows that Methylcobalamin can selectively increase immune cells that kill cancer and improve other diseases- I consider that 'good'.

These are only a few of the studies that I found. There are many more.

Kerri Knox RN Immune Health Queen

Kerri Knox, RN- The Immune System Queen
Functional Medicine Practitioner
Immune System
Side Effects

B12 Side-effect - Pain In Right Lower Abdomen
by: Chris

I have got a pain on the right-lower-abdomen. It is much below the end of the rib-cage, near the end of the stomach, right between the front and the back, in line with the navel / belly button.

Sometimes the pain is on the left side, but most often it's on the right side which is always present even when the left side is hurting.

It started a month ago since the same day I started taking oral Methylcobalamin (1 tab, 500 mcg). I also took Natrilix SR (Indapamide diuretic for BP) on the same day and continued it for 10 days before stopping it. The pain was there on all the 10 days.

The pain comes and goes during the span of a day. On a day when I take more doses of B12, the pain is more acute, though not severe. It is more like a light pain that is more irritating than painful.

The pain does not stay there constantly. It isn't there in the morning as I wake up, but comes only after any food or milk is consumed and subsides to a lower dull intensity after some time. I am heavily constipated, but have always been even before the pain started.

I have stopped taking oral B12 (either sublingual or swallow) since some time and gone back to getting shots. I still do benefit from it as my eyes gets tired less easily. But the pain is still there even when taking injections.

Could this be a side-effect of B12 oral supplementation or injections? What could be the affected organ in this affected region? Any blood tests that I should get done?



by: Kerri Knox, RN- The Immune Queen!

Hi Chris,

I've never once heard that as a side effect of B12. Not to say that it's not, but I've never heard of it. The right side of your belly is the appendix and part of your colon.

If you are hurting there and you have chronic constipation, then you NEED to take care of the chronic constipation- regardless of whether that is the cause of your pain or not.

Please read my page on Signs of Magnesium Deficiency as constipation is nearly always due to magnesium deficiency- and high BP is as well. Also, the diuretic could be depleting your magnesium making this worse.

If you have both Vitamin B12 deficiency and magnesium deficiency and constipation, the chances that you have Gluten Sensitivity are extremely high- whether you have any of the 'classic' symptoms of gluten sensitivity or not and even if you've tested negative.

Kerri Knox RN Immune Health Queen

Kerri Knox, RN- The Immune System Queen
Functional Medicine Practitioner
Immune System
Side Effects

by: Chris

Thanks for the reply Kerri.

from: http://www.diethealthclub.com/health-issues-and-diet/appendicitis.html
"Appendicitis pain may also increase when you apply pressure on the region."

a) I don't feel any further pain on pressing on the region. And sometimes I feel the pain on both the sides of the stomach. So it may be related to gas or constipation. But could it be the kidneys? (I am off the diuretics are those 10 days)

b) I have read your Gluten sensitivity pages. Although the blood tests may not be conclusive, I would still like to do them in case my allergy or even Celiac shows up in them. Can you please let me know which blood tests are done for it? I couldn't find the names on your pages.



Not likely appendicitis
by: Kerri Knox, RN- The Immune Queen!

So, it's not likely to be appendicitis after almost 2 weeks, but you asked what could cause pain in the right lower side of the stomach and that's one thing.

With chronic constipation, it's almost certain that's the problem. Why it would have come on when you started b12 is a coincidence maybe? Or a mystery?

Having chronic constipation is VERY VERY bad for your health and should be remedied ASAP by every means possible.

As far as gluten testing, I don't know the names of the tests and you'll have to research or ask that on your own because I want nothing to do with helping people get tested. Once you start getting into the rabbit hole of testing, then you spend thousands or tens of thousands of health care dollars just so you 'know' and the vast vast majority of the time it comes back negative and then you are confused, worried, don't want to try a gluten free diet, your doctor told you that it would be useless and thinks your crazy to go off gluten, etc.

Personally, my belief is that it's wrong to spend so much money just to 'know for sure' when:

a) You probably won't end up knowing for sure
b) You will get MORE information by just going off of gluten at zero cost to the health care system.
c) By going off of gluten and sensing how you feel, then you will begin to learn to listen to your body and what foods agree and disagree with you and that will do you FAR more good in the long run than any testing

So, I won't judge you if you feel the need to get testing, but you're on your own and I can almost guarantee that you'll be FAR more confused and even potentially have some difficult decisions to make such as whether or not to get an upper GI endoscopy with a biopsy- since that is the 'gold standard' that gastroenterologists use before they will give a diagnosis- even though a recent study showed that people with mild gastrointestinal damage (who will NOT get diagnosed with Celiac Disease and will be told to eat as much gluten as they want to by their doctor) who still continues to eat gluten has a shorter lifespan than those without any gastrointestinal damage.

Also, many people who are gluten intolerant are lactose intolerant too- a VERY common cause of constipation. There are no tests for that, so how will you determine if you might be lactose intolerant?

So, if you are going to go on a gluten free diet whether you are 'positive' or 'negative', whatever those labels mean, then why spend several months and thousands or tens of thousands of dollars to do it? It's up to you, but I won't help you by answering any questions about testing, etc. But if you want to just go off of gluten, then I'll be happy to help.

by: Chris

I am thinking of doing the Hypochlorhydria (low stomach acid) test by taking Betaine HCL.

I tried having tea (caffeine gives me instant acidity any time of the day) after lunch to create acid in the stomach and it gave a heartburn. Should I still do the HCL test?

If that doesn't solve the problem then I will do the Gluten Intolerance test by getting off it which seems quite difficult to do since it's everywhere.



You are not eating Food
by: Kerri Knox, RN- The Immune Queen!

Hi Chris,

Sure, go ahead and try the hypochlorhydria test, HCL is good for you and I take it once in a while just to keep my HCL levels up in my stomach even though I have no heartburn, no acid reflux or trouble digesting.

If you think that going gluten free is going to be hard because it's 'everywhere' as you said, then you are not eating 'Food' anyway and should seriously work on your diet- and that is probably the main reason that you have chronic constipation, you are not eating 'Food', you are eating non-food. Gluten is only in 'non-foods' but it is not found in 'food'.

So, if you ONLY eat FOOD, then you will have no trouble not eating gluten. For example, there is no gluten in:

Animal products
Coconut oil, olive oil, butter, lard

If you stick with these real foods, which are essentially the only foods that I ever eat and are the only things that should even be CALLED food, then you'll have no problem. If you just don't buy ANYTHING in packages, jars, bottles, cans, boxes, etc then there are no labels to read and no hidden gluten to worry about. FOOD does not have gluten, only non-food has gluten.

Kerri Knox RN Immune Health Queen

Kerri Knox, RN- The Immune System Queen
Functional Medicine Practitioner
Immune System
Side Effects

Vegan forum biased
by: Anonymous

I'm a vegan of 21 years and in the last 5 years have had low D and low B12, tested at 210. Symptoms I have had which respond to B12 are constant irregular heart beat, electric shocks running thru whole body inc heart, irregular BP, dizzy spells , upper right abdominal pain with periods of no bile, constipation, extreme muscle shaking, no energy & a host of other horrors.
I made the mistake of reading the advice on the vegan forum & it led me to waste 3 years of my time going down the wrong path, bad advice that could have cost me my life.

Vegans want to pretend that B12 is not needed in any quantity and is not really linked to any disorder at all, as if this is all some plot to prevent them being vegan. B12 from my experience is a cornerstone vitamin, without it magnesium does not seem to work properly in the body. Without it the nervous system starts to degrade & MS like symptoms and other horrors follow.
The vegan forum is wishful thinking replacing a reality in which B12 deficiency is an absolute mortal danger.

The vegan diet is not healthy, and I can say that because I am a vegan. The vegan diet without B12 supplementation will leads to sickness and death.
Vegans are generally a group of people pushing a very misguided diet & their advice on B12 is shaped to fit that deluded diet & should therefore generally be completely ignored.

No Upper LImit for Methyl B12
by: Siri Peterson

I currently take 100,000 to 150,000 mcg of Methyl B12 (sometimes combined with adenosyl B12). Jarrow Methyl B12 lozenges were fine until I st
s Methyl B12 5 mg tablets, sublingually, between upper teeth and gums, usually at night. Sometime during the day, when I can, I take Adenosyl B12 -- around 4 times a week. Since I actually don't trust the supplier on consistency and quality of product, I won't recommend them by name.

I now have some enlarged red blood cells (MCV count), and *not* having methyl b12 for two days during a recent hospitalization produced cerebellar ataxia. Back on Methyl B12, and I'm ok. I have fought various wars with MDs over the years, and just kept taking methyl b12, because it healed my peripheral neuropathy that made my legs completely numb, so I would fall over frontwards like a tree, and bang my head. Very not good!! I started Cyanode Cobalamin in 2004, about 1,000 mcg four time/wk. Graduated to methyl b12 in 2009; lost my chronic IBS, and gradually was able to wiggle my toes again. I still can. i am now coping with some ataxia when methyl b12 levels are low, so it's not all roses.

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