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Pernicious Anaemia Society
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Checking b12 levels while supplementing?

Hi all,

I have a conundrum ... pls scroll down to my Q at the end if you don’t have time to read my backstory ☺️

I have hypothyroidism but I haven’t been diagnosed with PA, and IFa test came back negative. I know this could still mean I have Pa but I don’t have the fight in me to argue with Gp.

I had low levels of b12- always been 160-240 in the few years that I’ve had it tested. When I’m on hormonal/contraceptive tablets it’s lowered it further and I used to feel I was dying.

Long story short I had loading doses injections in February and my symptoms disappeared (neurological and fatigue etc)

They slowly crept back in a few weeks after so I took 3000iu oral spray daily - seemed to manage most of symptoms but about a month ago they got worse again- and then I started hormonal ivf meds which made it worse (not as bad as before thankfully maybe because immsupplemeting) however I’m due my 3 month injection in couple weeks (doctor said I didn’t need it nurse said I did so Im hoping they will agree to do it as I def feel I need it!)

However i want to check if my b12 levels are ok whilst on the spray so I’ve ordered a blood test online which I’ll take on Monday. I know b12 levels can be skewed whilst taking supplements but that’s the whole point- I want to know if my active b12 is ok whilst on supplements I’m taking.

1) So my Q is- do I take the spray as normal (at night) and test in morning?

Should I stop taking the spray at least a day or two beforehand so that an immediate spike isn’t skewed by the sprays but it still gives me an idea of supplementing is working?

2) is it ok to have b12 injections whilst possibly pregnant?

Thanks in advance ( I feel my last ivf failed partly due to undiagnosed b12 deficiency and don’t want to risk it again- so frustrated that ivf has timed with my 3 month injection and my symptoms returning

16 Replies

to be honest I'd not advise testing at all after you start loading doses - though it may be useful to one test to see how your levels have dropped since the shot.

You need to go by symptoms.

A day or two of not supplementing isn't going to make any material difference to the blood test - recommendation is to stop for 3 to 6 months if you want a base line. All serum B12 tells you is how much there is in your blood - it doesn't tell you whether that B12 is getting through to your cells and whether it is being used efficiently in your cells - active B12 is pretty much the same at this point.

B12 isn't toxic so high levels in serum post loading shots aren't a problem. I'm not a medic but I'm not aware of anything that would preclude using during pregnancy - more likely to be problems from being deficient during pregnancy.


Thank you for your reply!

I was thinking of testing to see if I’m even absoribing the b12 from the sprays and I thought active b12 would give better idea if it’s actually reaching the cells??

I thought thats what active b12 was more or less 😣

It’s also to show doctor if my levels still aren’t great even with 3000iu spray daily that I Might actually have a problem!

However if the results are ‘normal’ then I will probably look to sub lingual etc or injections myself long term to see if symptoms improve.

Thanks again


B12 in your blood is bound to different proteins - one that allows it to pass into tells and others that enable it to be stored in your liver or removed from your body. Active B12 measures the amount that is bound to the protein that allows it to pass into your cells but that doesn't guarantee that it is actually getting into your cells.

Active and serum B12 are reasonably good guides to absorption problems as levels will be dropping if you have an absorption problem but they aren't really good measures of what is happening in your cells. There are a couple of test that may give a better guide to what is happening in cells - namely MMA and homocysteine - products that build up if your body doesn't have, or can't use B12 efficiently (rare genetic factors) to run the elements of processes in your cells that recycle them to useful building blocks.


Ahh thank u so much !

I had heard of the MMA ad homocysteine and mthfr? Gene mutation on this forum but that above explanation links it together perfectly for me.

I’m hoping I don’t have an issue with that as my problems have only surfaced in recent years and I think it’s thyroid related rather than PA (or I hope so!). I was given hydroxycobalamin injections and felt brilliantly after so I’m assuming I don’t have a conversion issue?

Can u get mma and homocysteine checked with online blood tests? I didn’t see it on medichecks website

Thanks again.


St Thomas's in London do the tests but I'm not sure of the process - they are more specialised tests which is probably why they don't appear on medichecks on-line.


Thank u very much for all your thoughtful replies!

I’ve done a lot of reading around on this forum but sometimes it just feels like an uphill battle- even if I know what to do- do I have the energy to fight for it?

Thanks again- I won’t bother you with more questions ☺️


It is completely safe to have your injection while pregnant. I had mine all the way through my pregnancy i even had consultants who kept an eye on how i was feeling incase i needed them more often 😀

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I did wonder - those with PA would obviously need it throughout pregnancy so it must be safe (it’s not toxic anyway) but I wanted to be sure in order to mitigate any resistance by nurses or doctors to treat me! Thanks

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B12 deficiency can certainly lead to difficulties with conception .


That’s what I’m so upset about because I feel like this made my initial ivf cycle much more difficult.

I thought the injections and sprays were working so I continued but it just turned out the injections only lasted 2 months and it’s been wearing off since. I hope they’ll agree to earlier injection. (By 10 days only!) but knowing the jobsworths at the surgery getting through to them will be difficult. 🙏


Have you considered self injection ? In desperation that’s what I had to do , and I bless the day that I did . It’s cheap and easy honestly . You cannot overdose . You learn from experience how often you need to inject .

I know it should not be necessary, but with such ignorance abounding in the medical profession about the subject , it’s the only way out at the moment . It is totally safe for you .


Yes from now on I think I will. I actually thought the spray was working- might give sublingual a go in the meantime. I’m rushed for time as ivf treatment transfer is this week (!) horrible timing - but will look into self injecting


You would get lots of support from us all 👍🍀

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There has been indications that overdoses of b 12 whilst p pregnant can increase the risk of autism in the foetus. Please only take what the doctor prescribes whilst in ivf and pregnant.


Oh wow I’d never heard of that.

Generally it’s pushed that you can’t really

Overdose on b12 and no dangers.

I still don’t really know what to do as GP surgery are clueless themselves. Might check again myself



The issue is that there have been no safety tests on b12 to find the maximum safe tolerated dose, so no one can categorically state that too much b12 is unsafe. There have been observational studies where some theories were generated, but they really need an interventional study to say anything definite.

Ivf requires the doctor to know exactly what is going on in your system, maybe worth postponing SI for now?

Have you tried registering at a different surgery? See which others are available for your area or request a referral to a specialist, they can't refuse to refer you.


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