How much are your levels supposed to rise to after getting your loading injections?

Hi, I was diagnosed with PA with a b12 level around 140 (150-900). I had 6 loading injections over 2 weeks and 6 weeks after my last loading injection I had my b12 tested again and it came back as 565 (180-950).

Is this a good amount of b12 to have 6 weeks after loading and 6 weeks before my next injection? I have read that some people's b12 levels shoot way up after getting these injections and it has me concerned that perhaps my b12 levels are going down too fast or am I being paranoid?

Can anyone else tell me what their levels were after treatment and how they found it?


PS I never had symptoms of numbness or tingling so at the time 6 injections sounded like enough

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3 Replies

  • Hi Carly,

    Its very different per person what their serum levels are after a B12 injection, some can end up with serum levels over 1400, others may only get to 300, symptoms per persons are different some feel well with serum levels of 300, others need it over 1000 to stay well. No rime or reason, no clear answers to give, it all depends what your body does with the injected B12, so much more goes on after its reached your serum, a lot of other things can go wrong or slowly wrong, some may still store others may not, some may recycle others may not some may convert well to the 2 active forms the body uses others may not or not that well etc, so no clear answer can be given. It depends on how you feel, and if other B vitamins (particularly folate and B6) and iron are in good supply as well.

    Perhaps read this, it may give you a bit more understanding, see:

    I hope this helps a little, its how you feel that is important.

    Kind regards,


  • There is a huge amount of variation in how long people retain hydroxocobalamin.

    I can't remember the exact percentages but the amount that you lose in the first 24 hours is huge (50%+) - even the amount lost in the first hour is pretty astounding - but it does seem to be a curve rather than a straight line.

    Its also well established that the serum B12 test isn't a good guide to whether you are experiencing problems because of B12 absorption - hence the current recommendation in the UK to treat on the basis of symptoms rather than test results (though the guidance on what treatment is needed is still something that needs work).

    What symptoms people have also seems to vary very much - only constant is that left untreated all will occur at some point on the way to .... but you are getting treatment. This doesn't mean that the treatment you are getting is sufficient but the way to establish that is to monitor the symptoms not to look at the test results.

    What levels their B12 needs to fall to also varies - which is partly because the test is looking at total B12 and not active B12 - levels of which could be very different.

    Having said all of that to have fallen to around 500 within 6 weeks does sound as if you are one of those people who has a short 'half-life' for retaining hydroxocobalamin.

    Suggest that you KEEP A DIARY OF SYMPTOMS so you can follow up on that with your GP if necessary - though getting through to them that it is symptoms rather than test results might be a different battle - at least if you can demonstrate the symptoms it is a battle that you can start.

    Are you due to have another serum B12 just before the maintenance shot - that would be really interesting.

    If that is low and your symptoms have come back significantly before your maintenance shot then that is the point at which to think about whether there may be other factors involved.

    Your anxiety could be a symptom of B12 deficiency and it may be that for you it is the neuropsychological symptoms that are the real indicators of how the B12 is affecting you. I find that my neurophysological start to return within 24 hours of a shot which is why I use B12 at high levels on a daily basis - today was the first time that I'd had results back on a serum B12 test since I was diagnosed - and came back as above 2000 - but as I'd taken 2.5mg nasally a few hours before the blood test (blood test wasn't preplanned) I'm not surprised and fortunately it hasn't got any red flags on part of GP, which is how it should be.

    The important thing to remember is that you cannot overdose on B12, so additional supplementation wouldn't be a problem if it is needed and you are in a position to afford to source it personally.

  • Hi Carly,

    Re: "Can anyone else tell me what their levels were after treatment and how they found it?", I found my serum B12 never got very high on standard treatment. I find I'm not that well if its serum B12 230 ng/L = 170 pmol/L. Folate 2.1 ug/L (standard treatment), felt best with: serum B12 548 ng/L = 404 pmol/L Folate >24 ug/L (daily 5 mg folic acid and weekly cyano plus 2 monthly hydroxo), was dismal ( thought I had mad cows, jelly legs, weak and cotton wool brain) when diagnosed with: serum B12 86 ng/L = 63 pmol/L.

    But it is so different per person, and folate and or iron def does not make you feel well either.

    Kind regards,


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