Pernicious Anaemia Society
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Is my Vitamin B12 reaching my cells?

Hello Everyone,

I have hypothyroidism and pernicious anaemia. After much frustration with the NHS I am now practically self treating both conditions. I am feeling unwell again, tiredness, nausea, headaches, cold hands and feet. I don't know why but feel the symptoms are more pernicious anaemia than thyroid, although I know when one is out of sync it will affect the other.

I inject myself with B12 injections every two weeks. I am not noticing any difference in my symptoms after I inject.

My questions are :-

1) How do I know if the B12 I am injecting is enough, do I need more? some people inject daily, how do you know if you need more?

2) If the B12 is reaching my cells? Just because there is more than adequate in my blood, does that mean that amount is reaching my cells?

3) How does a person know if they would fair better on the active B12 injection, Methylcobalamin?

4) Where can I go for help with this? I am going to arrange to have a B12 blood test with Blue Horizon that will show my current B12 levels.

I would be so grateful for any help or assistance on this.

Many Thanks,


11 Replies

There are people on the forum who know more about this subject than I do and hopefully they will be along shortly. I can't answer your question about how B12 reaches your cells (still learning about all this), but the only way you can know whether you are better off injecting hydroxocobalamin or methylcobalamin is to try each in turn.

Start off with a small dose, on alternate days perhaps, and take note of changes to any of your symptoms. If there seems to be improvement after a month say, carry on until there is no further improvement and then reduce the frequency of injections down to a maintenance dose that seems to hold things steady.

Some on the forum take both types of B12 at different doses and intervals to treat different aspects of PA or B12 deficiency. You have to experiment. I find I have to inject methyl daily, and in much higher doses than I ever anticipated.


Hi Hillwoman,

Thank you very much for your reply, it was really helpful. The amount I inject at present is 1ml equivalent to 1000ug's once every two weeks. I just realised it is cyanocobalamin, don't know if that is better or worse than hydroxocobalamin, any thoughts?

Can I ask? If you're injecting B12 daily, how does that affect your blood work?

The last B12 blood test that I had last year, I was told that I was over medicating but I still continued to inject fortnightly. One would think if you're injecting Methyl daily, your blood would be full of B12?

I'm really interested to know, as per my initial question, how do you know if you're getting enough? if your blood tests say you have sufficient but you still have symptoms?

Is it dangerous to overdose on B12 injections? Sorry for all the questions but I am really feeling quite unwell and desperate but don't want to do anything that will harm me.

Thanks in anticipation,



Annie, please don't worry about toxicity or overdosing. It's possible to overdose and cause yourself harm with other B vitamins, but there is no reliable evidence, so far as I know, that this can happen with B12. I have recently been advised by a doctor I consult privately that I should not worry about toxicity, and though her advice was to me and not to you, the principle still holds.

I know some on the forum think that cyanocobalamin is probably the worst of the available injectable options, because:

1) it may be possible to have too much of the cyano part of it;

2) it is an artificial form and may not be assimilated and metabolised by the body in the same way as hydrox or methyl.

Taking supplements close to blood test is not a good idea, because your results will lead your doc to think you are fully supplemented when you are still symptomatic. I no longer have blood tests for PA, but that is another story. You are properly treated when you are no longer symptomatic.

Standard blood tests for B12 levels are very crude, and the lab ranges are broad. Try looking up the 'active B12 test'. As I say, I'm still learning about all this. You could also try sending a PM to Marre on the forum, though she may be away at the moment. A lot of other people here are helpful too, but things are quiet at the moment, so you are stuck with a learner like me! :)

Don't hesitate to ask further questions.


I should also say that symptoms may become worse temporarily if you are not also adequately supplemented (with food sources or actual supplements) with methylfolate (NOT folic acid, which is difficult to metabolise), vitamin D3, the other B vitamins, and iron.



Thank you so much for your quick response. I am feeling desperate at the moment so just ordered some Methycobalamin from Oxford Sciences. Can I ask where you get your Methyl from?


I've read here that the Oxford Bio methyl is good stuff, but you will need sterile saline to dissolve the powder. The necessary links are on their website. I get my methyl from a charity, The B12 Deficiency Support Group.

However, at the moment they're in financial difficulties, so they're awaiting more donations before they can order any more methyl. I would go with the Oxford stuff for now.


Usually the deficiency is treated at first by having 6 injections in 2 weeks then 1 maintenance injection per x amount of weeks, it seems to really depend on the individual on how often they need maintenance injections. It can take up to 3-4 months to feel better and for you to recover, it personally took me about 6 weeks. You just have to give it a bit of time. As you are injecting the b12 it will be reaching your cells and being absorbed effectively. If you arrange a b12 blood test do it as long as you can after the injection, ideally just before the next time you inject.


Unfortunately there is no way to know if the B12 is reaching your cells, other than your health, i.e. is it getting better or worse? Likewise, that's the way most people 'test' how often they need an injection - purely on how well they feel and which injection rate is optimal for them. Certainly though there will be more than enough B12 in your blood if you are injecting every fortnight.

When did you last have your thyroid tested? Are you sure it's not got out of whack again? You say you are practically self-treating both conditions. It is possible you could do with some professional input here, and even that you are maybe over-medicating? Not because B12 will be, per se, toxic, but if you keep upping the dose of both medications I imagine you will start to feel poorly because your body will be struggling to cope with too much of everything! And thyroid meds definitely ARE toxic if not done correctly.

I know it sounds counter-intuitive but perhaps you need to take a breath and actually slow some of your medications down. It sounds as if you are getting desperate and throwing more and more at the problem because you feel more is better. Sometimes it isn't. Maybe just have a breather and get some actual concrete tests taken to see what your actual B12 and thyroid figures are and then, armed with that, you can either consult a doctor or if you don't feel happy with that, just ask for advice on the corresponding forums. With actual figures to deal with people will be able to give more concrete advice.



I also control my own conditions - hypothyroid and PA. Blood levels for PA are useless, as mine were (off the scale) meaning over 2000 and I had PA!

I am presuming that your thyroid is controlled very well so I will not make any comment with regard to that. My only advice would be with regard to your adrenals, however that is another medical condition and at this time I will stick to what you have asked about.

I would definitely not use cyano for my B12 intake, my personal preference is methyl or andenosyl, however we are all different so that is up to you.

You ask how you know if you are getting enough B12? The best answer I can give you is that when you have enough of the correct cobalamin - you will feel great...honestly. As I say, I am presuming you only have the conditions stated and there are no other complications.

Without getting too technical, the cobalamin you take in (eventually) goes into the methylation cycle (metathione) and interacts with the folate cycle amongst others. It would be worth getting yourself supplements which comply with the MTHFR mutation. By this I mean 5-MTHFR-folate rather than folic acid and pyridoxal-5-phosphate, or P5P for short instead of B6. My point is that you need to give your body as FEW problems as possible to have to encounter and deal with. The advice I am giving you will be fine whether you have this particular SNP (mutation) or not. It won't matter, however it is a better way to get vital nutrients into your system.

If you wish to read more on this please go to Dr Amy Yaskos site, however it can be a little mind boggling especially if you are not feeling too well at the moment. I would echo the sentiment of others and suggest you get a professional to assist just for the time being, until you get a bit better.

I don't like to think of you struggling with this and still not feeling good.

My very best wishes.


Hi KateMelissa,

Thank you very much for your helpful post. I am actually feeling so much better since I wrote this post but it has taken me a while to work things out. I realised that Cyanocobalamin was not a suitable cobalamin for me. I am now injecting with Hydroxocobalamin on alternate days and that seems to be doing the trick, thank goodness.

I am very interested to learn more about the Methylation process and how that may be affecting my health, so I was very interested in your comments on that. I am currently seeing a nutritionist on a regular basis and she has suggested genetic testing at some point. Together we are going to look at everything this year so that I can fully understand how to support both conditions through making changes to my diet, adding in supplements etc. etc. The first thing we are looking at is how well my digestion is working, and whether I am absorbing nutrients well from my food.

This is my project this year, I am determined to get on top of my health.

Thanks again for your post, I hope you are feeling well :-)

Best Wishes,


Hi AA,

I am so pleased you are beginning to feel better.

I am sorry to comment so late on your original posting but I must have missed it.

I do admire you for taking charge of your health - hopefully this year will see a definite improvement for you once you get on top of things.

Anything interesting you learn with regard to methylation, I would be really grateful if you could pass on to me. I am always interested to improve on my education in this area.

Good luck with everything, keep improving and my very best wishes.


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