Can too much of B12 be harmful?: Happy new year... - Thyroid UK

Thyroid UK

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Can too much of B12 be harmful?

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Happy new year to everyone. I have a question, hope someone will be able to help. Just before 31 Dec I got blood results for vitamin B12. I have 1467 while the reference range goes from 141 to 489. I was getting B12 injections for 3 month but it was last summer. So obviously I have too much of it in my blood now. Why is this since months passed since my injections and can it be dangerous. Thanks.

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Vitamin B12

29 Replies

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humanbean8 years ago

That reference range is absolutely unbelievable! It's the lowest I've ever seen!

Having a high level of B12 is not poisonous and does no harm at all. Mine is over 2000 and I feel better with that level than I did with a level which was in range.

in reply to humanbean8 years ago

Good, I am relieved. I though there was something wrong with me.

Fruitandnutcase in reply to 8 years ago

Mine was over 1100 the time before last when I had it tested in July 2015 and the report said "The Vitamin B12 level is elevated. This is not likely to represent significant overdose, as B12 is well tolerated by humans even in very high concentrations, and is usually a result of supplementation or following a diet rich in the vitamin. Some advocate high doses of Vitamin B12 to combat the development of Alzheimer's disease."

I had a little B12 holiday and when I had it checked again in early December 2015 (I've just gone GF and wanted to see what my antibodies were up to, I don't normally test that often) my B12 dropped to 388 so I've started it again.😊

in reply to Fruitandnutcase8 years ago

Thank you. I was really scared when I got the results, I though I took too much. It's good to hear from people who have the same experience.

8 years ago

Hello Simona,

The Pernicious Anaemia Society advises Vitamin B12 is a water soluble vitamin so the body excretes excess amounts in your pee making it difficult to overdose or build up vitamin B12 toxicity.

I have high levels too.

Flower

pernicious-anaemia-society....

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Disclaimer: I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.

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in reply to 8 years ago

Thank you for the link Flower. I feel so much better now knowing that it is normal.

8 years ago

No it's not dangerous. If you have pernicious anaemia do not stop your injections. Never. Serum b12 levels are unreliable.

You only have 20% of that total serum available.

Mine is 2000 +. And I will keep it up. It's water soluble, none toxic. Your body excrets what it doesn't need. Can only help you and keep you well.

Stop worrying and have your b12.

in reply to 8 years ago

Thanks. So you have even more of it than me! It seems that those tests don't have any purpose, I just got scared for nothing.

in reply to 8 years ago

I understand, its good to be concerned like that. The tests are important to know but , now you know more and its for the better. You can make the best choice now.

in reply to 8 years ago

Thank you so much x

in reply to 8 years ago

Simona,

The serum B12 test that GP's do result in a measurement of "active" and "inactive" B12 (holohaptocorrin) so theoretically only a very small % would be relevant and that is why high levels do not matter.

You will get a better idea of useable B12 at cellular level (aka holotranscobalamin) by taking the HoloTC B12 test.

This is available at St Thomas' hospital in London with a GP's referral.

Alternatively you can use private labs (link below).

Flower

Active B12 test.

thyroiduk.org.uk/tuk/testin...

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in reply to 8 years ago

This is very interesting and thank you so much for explaining. I wasn't aware that there was active and inactive vitamin B12. So it's something similar like when we measure FT3 in our blood and it can be normal or elevated but it doesn't show us how much of rT3 (so inactive T3) is in it?

in reply to 8 years ago

Simona,

No but it is the same as Total T3 and the amount of Free T3 that is actually used on a cellular level.

Reverse T3 is a different hormone converted from excess (unusable) T4 and we all need a little but too much is detrimental.

Flower

in reply to 8 years ago

Sorry Flower it seems that I mixed things. What I wanted to ask is - is the situation with B12 similar to the thing that we have useful T3 and not that useful rT3? Can too much of this inactive B12 cause us problems same as too much of rT3 can?

in reply to 8 years ago

Simona,

The common belief is no. There are authorities who advise to keep B12 levels over 1000.

I keep my Vit B12 high due to genetic variations that don't allow me to metabolise well.

I have found (only) one site advising of high Vit B12 side effects which are rare and even this site advises to high dose. I do not know the authenticity of this site either.

In view of the huge reprecussions of a B12 deficiency I consider it safer to high dose as also appears to be general opinion.

Flower

B12 overdose

newhealthguide.org/Vitamin-...

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in reply to 8 years ago

Thank you Flower. I read what was written on the link and I think that you are right, it can definitely be more beneficial to have it than there are chances that I will get leukemia or cancer because of too much B12. It seems that whenever they don't know what to say they put "it can cause cancer".

humanbean8 years ago

This page on high levels of B12 is very interesting and is worth reading :

stichtingb12tekort.nl/weten...

I particularly like this quote from the link :

The safety of vitamin B12 treatment is further illustrated by the decennia-long use of hydroxocobalamin as an antidote for cyanide-poisoning, often because of smoke-inhalation. In the Netherlands ambulances, fire-departments and emergency-rooms have the Cyanokit at their disposal. In life-threatening situations 5 mg hydroxocobalamin is given intravenously within 15 minutes, an amount that corresponds with 5000 injections of 1 mg B12.10 Hydroxocobalamin reacts in the body with cyanide, and forms cyanocobalamin, which is excreted in urine.

The serum value of B12 can rise to an average of 560.000.000 pmol/L within 50 minutes.11 If necessary this treatment is repeated within several hours, making the total dose 10 grams. The side-effects that occur, like reddening of the skin and urine and changes in heart-rate and blood-pressure are temporary and harmless. In short: 10000 injections a day are still not enough for an overdose of vitamin B12.

in reply to humanbean8 years ago

Thank you. This is very educational. You know, we always assume that too much of anything is harmful. When I got my results I searched a bit and found an website saying that too much of vitamin B12 in blood is a sign of lymphoma or skin cancer! Don't know where is the point of such writings that don't have any other purpose but to scare people. Thanks again for this.

humanbean in reply to 8 years ago

There are cases where a high B12 can be a sign of something being not right.

qjmed.oxfordjournals.org/co...

Life is never simple...

in reply to humanbean8 years ago

Yes, what I saw on the internet was probably abstract from this study. They were mentioning liver disease as well. How can I know now is this excess vitamin B12 sign of some disease in my case or not?

humanbean in reply to 8 years ago

I don't know the answer to your question, sorry. Do you have recent blood test results showing liver function tests?

Have you ever supplemented with anything artificial which contained B12 e.g. a multivitamin? Do you have a diet which contains fortified food high in the cyano form of B12? Even things like breakfast cereal are fortified with B12 in this form.

Don't forget when checking, that B12 comes in four different types : cyanocobalamin, hydroxocobalamin, methylcobalamin, and adenosylcobalamin.

en.wikipedia.org/wiki/Cyano...

en.wikipedia.org/wiki/Hydro...

en.wikipedia.org/wiki/Methy...

en.wikipedia.org/wiki/Cobam...

My theory, for what it is worth (approximately nothing, I suspect) is that I have unwittingly taken cyanocobalamin during my lifetime in many different products including multivitamins and breakfast cereals, frozen meals, processed foods etc. I've been eating cereal for breakfast for most of my life. But what I'm not sure of is whether or not I can convert cyanocobalamin into the active versions of B12 that the body can use.

I suspect I can't convert the cyano form of B12 to the methyl form of B12 or the adenosyl form. So it sits in my liver doing nothing but has given me high B12 readings in testing. What I supplement with now is methylcobalamin and (very occasionally) adenosylcobalamin/dibencozide, and I feel much better than I did before. I also take the active form of folate - methylfolate.

Have you ever come across something called the "methylation cycle"? Please don't ask me anything about it, because I couldn't explain it to save my life.

drmyhill.co.uk/wiki/CFS_-_T...

I wonder if my methylation cycle doesn't work properly. But to do the necessary testing is beyond my budget. I'm planning - at some point - to follow the protocol laid out by Dr Myhill to improve my methylation. Whether that will reduce my B12 levels I couldn't say. But in the meantime I'm going to stick to my methylated supplements because they make me feel so much better.

in reply to humanbean8 years ago

Thank you so much for taking time to explain all this to me! I haven't done any liver tests recently. Before they were always fine. I do take multivitamins, I did that my whole life. Maybe it's from there? I eat cereals sometimes, but in last few months not that often. I was getting B12 injections last summer for 3 months, but person from the lab told me it should have cleared by now since I finished with injections in early September. I'll look at all the foods that contain what you explained, to see is there anything else that I eat that can cause this (except cereals). Thank you again x

humanbean in reply to 8 years ago

I bet your multivitamins have all contained cyanocobalamin. As I understand it, if you can't convert it to one of the active forms, it will get stored in the liver and will just sit there doing nothing much. Fortifed breakfast cereals may contain cyanocobalamin too.

If the methylation cycle is working properly then the body should be able to convert the cyano B12 to one of the more active forms that your body can use.

I do hope my wittering has some semblance to the truth, but I'm not making any promises!

in reply to humanbean8 years ago

Thank you. Yes, it all make sense to me. How do we know which multivitamins contain cyanocobalamin to avoid them? Is this written anywhere on them, or it is something known by brand or manufacturer?

humanbean in reply to 8 years ago

All supplements should have their ingredients listed on the bottle.

I picked a multivitamin at random from H&B :

hollandandbarrett.com/shop/...

and it shows "B12 (as cyanocobalamin)" as one of the ingredients.

in reply to humanbean8 years ago

Thanks. Just looked at mine and it says "B12 (as Methylcobalamin)". Is this form problematic as well? I take Eve multivitamins from Now Foods.

humanbean in reply to 8 years ago

Methylcobalamin is one of the desirable forms of B12 - it is in a form the body doesn't need to convert and so is much more easily absorbed and used by the body.