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Pernicious Anaemia Society
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Levels before injection

Hi what should our levels be roughly before an injection?

About 4 weeks before I start to feel gradually more sluggish (even when my thyroid levels are good) but my levels don't really reflect it.

I'm due an injection on Friday (12th week since last) and my levels are 154.7 (25.1-165)

Where when I feel well they are well over range.

Also, my gp mentioned last time I don't have to be on them for life (or my folic acid or vit d) just until they are back in range and the deficiency is corrected.

I haven't been tested to confirm PA but I told him my levels start to drop gradually once I've had an injection or if I stop taking folic acid or vit d.

I didn't understand how I won't need them for life? Now they're back within range will they just get to a point that they stop reducing and going deficient? I'm not vegetarian or anything so there's no reason for the deficiency in the first place. I'm worried they're going to stop them but if my level is still high in range when Im due an injection do I still need them?


10 Replies

If you have PA you need injections for life.

PA cam#t be managed on serum B12 levels because injections introduce one factor - your serum levels going above normal range - which makes normal range invalid as a measure (not that it is valid as a single measure before treatment starts either). Treatment should be based on symptoms but sounds as if your GP really doesn't understand how B12 deficiency works ...

you could try pointing him at the area of the PAS website specifically aimed at medical professionals


PA is a problem that stops the mechanism that allows you to absorb B12 from your food. Although humans do store signigicant amounts of B12 in their livers the mechanism for accessing this involves releasing the B12 in bile for reabsorption into your blood via the ileum - a mechanism that isn't working - so you may have a reservoir but the pipe leading to the house is leaking very badly so you can't use it.

This means that you are dependent upon the B12 that is in your blood - but most of this is removed over time by your kidneys. Raisisng serum B12 can cause a reaction in some people that means that the B12 stays in your blood but very little gets through to cells where it is needed - affects enough people for serum B12 not to be useful as a guide to need for maintenance doses after treatment starts.

If you can't get through to your GP then you may want to consider joinin the PAS and contacting them for further support.

Sorry that you are being treated so poorly - even more sorry that you really aren't alone.

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Thank you. I haven't been tested for PA I was just put straight on the injections by a different gp.

I'm just worried that they will see my results are high in range and think I don't need them any more :(


unfortunately its a possibility but all you can really do is cross that bridge if you come to it.

There are options, eg self treatment - and they are relatively easy to put in place.


Thanks, hopefully it won't.

Would you expect someone with PA to have low levels just before an injection?

Is it ridiculous that I start to feel more tired and air hunger about 4 weeks before an injection even though my levels are top end of range?



some do - particularly if they are waiting 3 months - but some won't. Sounds like you need injections earlier than you are but that doesn't mean serum levels will be low because your symptoms come back when your cells don't have enough B12 and injections can introduce another reaction that tries to block B12 from getting into your cells - you are okay if your levels are above a tipping point where enough trickles through. For some people - myself included - this level can be very high.

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Thank you.

I was well prepared to go and ask my gp for more frequent injections as I had symptoms yet my last thyroid results in Sept were optimal.

But this latest blood test have shown it's starting to struggle again. So I'm going to beg for another dose increase then see how it goes.

I think I'll also get my IF antibodies done.

Does this mean I don't need to keep getting b12 tested every time I get my thyroid tests done? It would save me a fortune.

How often would you get b12, folate and vit d tested?



yes, there is no real point in paying for serum B12 test when on shots for an absorption problem

There isn't, as far as I can tell, any sure way of knowing what leads to absorption problems if you have a thyroid problem - but PA is particularly likely if you have an auto-immune thyroid condition.

Please be aware that IFA gives false negatives 40-60% of the time depending on the precise test method - so a negative is a long way from proving you don't have PA - it can also give false positives if done too close to an injection/supplementation - again how long you need to stop depends on the test method and varies between 24-48 hours and 10-14 days.


It's all so frustrating!

Yes I do have autoimmune thyroid condition. As well as PCOS, folate deficiency and vit d deficiency.

I have been doing active b12 tests which is what was still high in range just before today's injection. Does it make a difference to serum b12 in terms of telling if I do or don't still need them?

I really don't want to be taken off them and it might not happen. It's just from my gp saying I don't need them for life it sounds like they'll stop them at some point in future.

But if IF tests aren't reliable, my mcv was normal 95 (80-99) (but that was 3 months after loading doses) and the other tests don't sound too reliable either then I don't know what I'm supposed to do.

Because unfortunately treating based on symptoms seems to be insanity to gp's in all of these conditions!


with B12 you have to listen to your symptoms - and treat as those start to come back.

I don't test B12 levels - I respond to my symptoms and I treat myself for the most part.

If your thyroid levels are optimal then it would suggest symptoms aren't related to thyroid so keep a diary of symptoms in relation to injections


They were optimal in September and I was ready to ask for more injections but they aren't anymore.

So back to making my thyroid happy before I can ask for the b12. It's one bloody long journey!

Thanks for all your help over the last year though I'd have been so lost without it :)


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