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Pernicious Anaemia Society
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High active B12 result

I'd be very grateful for some guidance. I've just received the results of my active B12 test done through medichecks:

>256 (25.10-165)

I am on three-monthly injections and my last injection was 10 weeks before the test. I haven't taken any supplements containing B12 since the injection.

My question: might the injection be enough to explain the result, or should I be looking into liver/kidney issues (I have autoimmune thyroiditis, and I know thyroid hormones and kidney function are related)?

Just to give full context, I was diagnosed with B12 deficiency in January 2015 with a B12 result of 158 ng/L (180-900) and started on injections. I also supplemented high doses (5mg per day, typically) sublingually for many months, but have not done so for the past year.

Many thanks for any help.


Eep! I meant also to mention that my folate looks a little low to me (at least, it's lower than it usually is):

14.87 (2.91-50)

I have no idea whether or not this is relevant to anything, but again, would be so grateful for any guidance.

8 Replies

Your folate level looks okay - its quite responsive to diet - but if you have an absorption problem then that may mean that your ability to absorb folate is also decreased. The normal range for folate is a much better guide than for the serum B12 test.

The high active B12 is almost certainly the result of the injections, so not something to worry about.

Serum B12 and active B12 results will both be pretty meaningless as guides to your B12 status now that you are on regular injections so if you are trying to monitor your B12 levels through the tests I would suggest that you save your money and don't bother.

Symptoms are really the only way of monitoring whether you have the right levels now, though I am aware that symptoms will overlap with thyroid, so using them could be difficult if your thyroid medication isn't quite right.

How did you feel when you were using the supplements and has there been any change since you stopped. If you find that symptoms return before an injection then that would be quite common and doesn't necessarily mean that your B12 levels have dropped below the normal range - just that the levels in your blood aren't actually the right levels for you.

Keeping a symptoms diary would be a good idea.

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Thank you *so* much for this, Gambit - it answers every question, plus some I didn't know I had. :)

I haven't actually noticed any difference since I stopped the sublinguals, except for the last couple of weeks before my last-but-one injection when I felt I had recurrent symptoms that seemed to indicate B12 was a more likely cause more than anything else. (Of course this was rubbished by the senior partner at the GP practice who told me off for booking my injection 4 days early and also insisted that all her other patients with B12 deficiency who report recurrent symptoms are imagining it and that the (classic B12) symptoms I mentioned aren't anything to do with B12. I'm both deeply grateful for the NHS and despair of it at the same time!!)

Yup, my issue with symptoms - which I'm sure I share with many others - is that I also have other issues (underperforming mitochondria and high cortisol as well as the thyroid) and I haven't yet been able to say with complete confidence that symptom X is down to condition Y. Not helped by the fact that fatigue is common across all conditions, and that is my overwhelming symptom. *wry grin*

Thanks too for the guidance re the folate and the B12 testing. I usually elect to go for the vitamin tests along with the thyroid when I can afford it, and B12 is rolled up into that bundle, but it's helpful to know that I don't need to keep testing it in future.


the diary might be the thing that helps you identify which symptoms may be due to B12. If you didn't notice the dip when you were taking the sublinguals then these could well be a good way of keeping your levels up between maintenance doses - though possible that a lower dose might also suffice, so you could try some 1000mcg tablets and see how you work with those as I think that might be a bit cheaper.

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Thank you for the suggestion. It makes a lot of sense; I've tried to keep a symptoms diary but haven't been anywhere near as disciplined as I should have been. I'm now making an early New Year's Resolution! :)

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Were you taking biotin?


Click my user name for recent post with additional link.

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I saw your recent post and have made a mental note for the future to avoid Biotin before tests - but had you not posted, I wouldn't have a clue. Thanks so much!


THANK YOU (My Active B12 was 224 and i needed to investigate. I take Biotin daily when i remember at a does of 12000mcg (very strong) presuming this is the indication for the raised levels.

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