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Pernicious Anaemia Society
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Unexpected high B12

I was diagnosed with pernicious anemia 16 years ago and take B12 shots every 3 months (in the last few years every 12 weeks). Last shot was on 12 June. On 6 July my annual blood test showed B12 at 1769. The doctor has decided not to give me the upcoming routine B12 shot in early Sept and test again. I am worried about the cause for high B12. It's never been this high. Should I get any other tests done?

5 Replies


I do not understand why GP is not giving you your B12 injection.

Are you in UK? If yes, it may be worth you joining PAS (Pernicious Anaemia Society).


PAS tel no +44 (0)1656 769 717

They can sometimes intervene on behalf of PAS members. There are stories on Martyn Hooper's blog about how PAS has helped members whose injections have been stopped.



Has GP explained why he/she thinks a level of 1769 is a problem? I suspect my own levels are likely to be well into the 1000s.

Link to article about safety of high dose B12


PA treatment is for life

PAS members can access a leaflet "Treatment is for life" from PAS website which they can give to GPs.


I am not medically trained just someone who has struggled to get a diagnosis.

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your B12 is high because the result was taken 3 weeks after a B12 shot so there is going to be a lot of B12 swimming around in your blood.

Whilst serum B12 may have some merits in telling your GP that you have a problem absorbing B12 from your food it doesn't tell him anything about what is happening at the cell level where B12 is used. The normal range for B12 does not apply after loading shots have done because it introduces a new factor and the test is only significant if it comes back low - indicating that you have removed the B12 that was injected into your blood quicker than the average. Injecting B12 raises serum B12 levels which in some people causes a response that shuts down the mechanism that allows B12 to pass from blood to cells (functional B12 deficiency. It can be overcome but raising B12 levels to the point where the reaction can't deal with all of the B12 and enough gets through to cells. This is likely to be one of the reasons why patients who are being treated with shots tend to need much higher levels of B12 to be healthy.

If you are based in the UK you need to draw your GPs attention to guidelines which are now that B12 testing is not necessary whilst being treated for B12 deficiency unless there is a reason to believe that the treatment is not being complied with - so basically your GP has wasted money doing the B12 test.

Treatment should not be dependent on serum B12 levels being low.

As Sleepybunny suggests, contact the PAS and also point your GP at the area of their website particularly aimed at health professionals


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The level should be high - that's what happens with the injections! My GP insisted on checking mine, and the result - 2000+ - came back from the lab with a note attached saying there was no point in testing B12 once supplementation had started.

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I thought 6-10 days after B12 has had time to metabolise, the count should be in normal range. I've been tested every year and have had B12 injections for 16 years, it's never been this high. In any case, you seem to hold the view that elevated B12 is not a cause to worry. I don't agree. As a minimum it should be tested again, as indeed my GP will do soon. I'd like to hear from someone who can throw some light on whether any other cause for elevation of serum B12 levels needs to be ruled out.


the link below is an article which talks about things that can cause high B12 - however I think that it really is very unlikely that there is anything going on other than the injections.

the amount of B12 you receive in a shot is about 3 years worth for someone who doesn't have a B12 absorption problem - people vary a lot in how quickly excess is removed by the kidneys but on average 40% goes in the first 24-48 hours. The rate at which it reduces because your kidneys are filtering it out as the levels get lower.

how long is it between your blood tests and the last shot normally ... and do your symptoms come back between maintenance shots?



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