Pernicious Anaemia Society
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Does this sound normal?

I was last given an injection of vitamin b12 on march 8th after being told I had a vitamin b12 deciency I had bloods taken after and was told I should be fine now my b12 had shot up to 1500 and it was prob all my diet so got referred to dietician.

I must admit after about 2/3 weeks I did feel a lot better my symptoms had gone

Saw dietician didn't think my diet was a problem as been a vegetarian for 19 years and hadn't had a problem before!

Since middle of May my symptoms have come back I'm getting numbness in my arm pins and needles and I'm soooo tired falling asleep in the day which is not great when I have 2 kids!

I had bloods on Monday just rung for results as my dr said she would test them in 3 months time!

I didn't speak to dr this is receptionist

So my b12 has gone from 1500 to 428 but nothing to worry about as it's in range (200-900) but what I can't understand is why it can drop so much in such a short sPace of time and nothing be wrong with me ???


2 Replies

Hi Al1985 being a vegetarian may put you at risk of developing a B12 deficiency as it can only be sourced naturally by eating red meats, fish, seafood, eggs, poultry and dairy produce and if none of these are included in your diet you will probably need to supplement, either by injection or by other means for the rest of your life - as is suggested and indicated by the return of your symptoms.

Make a list of them and go back to your doctor and ask for treatment.


a) dietary related B12 deficiency can take a very long time to manifest as the body is generally very good at storing B12 that it doesn't need and the daily requirement is quite small, so a dietary deficiency can take years to actually build up to a deficiency - so the fact that you haven't had problems for years doesn't necessarily rule out a dietary cause.

The correct treatment with a dietary deficiency would be oral tablets that are about 10x RDA taken daily. 50mcg cyanocobalamin.

However, unless you avoid dairy and eggs as well as meat and fish its unlikely that the cause of a deficiency is dietary - just because the amounts needed from diet are very small.

b) B12 deficiency due to absorption problems tend to develop very slowly but symptoms snowball towards the end.

Unlike the other B12 vitamins the body stores B12 in the liver and releases it in bile into the ileum for reabsorption as required.

The ileum is also where most B12 is absorbed ... and if you have an absorption problem then you have the double whammy of impaired absorption from your diet and a very leaky tap on the top-up tank. As absorption problems can take a long time to develop just how leaky everything is tends to build up over time - which can be years or even decades.

Please note that I am not suggesting that c) applies in your case but include it for completeness.

c) I am not a medic but I personally wouldn't recommend using an injection to resolve a dietary deficiency - nor would I recommend using doses higher than around 50mcg.

Raising serum B12 levels above the normal range may trigger problems elsewhere in the metabolism of B12 - basically kicking off an auto-immune response that interferes with B12 being transferred from blood to the cells where it is used - something that serum B12 test (and active B12 test) don't measure because they are just looking at what happens in the blood.

There isn't any clear protocols for treating the resulting cell level deficiency (functional deficiency).

One of the features of response to high level in serum appears to be keeping B12 in blood longer - it can take a very long time for levels to fall to a point where the reaction stops. Keeping serum levels really high does seem to work as a strategy though - I personally think of this as being like having a dam but still needing water downstream - so you have to keep the levels behind the dam so high that enough trickles over the top. However, trying to get this through to a GP can sometimes be impossible.

d) Trying to use serum B12 levels as a guide to B12 deficiency is hit and miss at the best of times - people vary a lot in how serum levels relate to what is going on in cells and the normal ranges will miss 25% of people who are deficient and pick up 5% of people who aren't as a result.

After a loading shot of B12 normal range becomes absolutely useless as a guide because the loading shot introduces a factor - discussed in c) which means that normal ranges will be completely different for someone who has had a B12 shot - and studies seem to show that on average people who are being treated with B12 shots need to have levels of 1000+ to feel healthy - so a very different set of circumstances. However, average GP is totally oblivious of this - they have a lot of other diseases to look at and ones that don't confirm to nice ranges tend not to be well appreciated. Besides B12 is only a vitamin and gets very little coverage on medical courses.

Basically serum B12 after a loading shot doesn't mean much unless it is coming back low and 428 is potentially low 3 months afterwards.

e) the body tends to be very good at removing excess B12 - ie beyond what it can store in the liver - quite quickly - and it basically ends up being flushed away. 50% goes in the first 24-48 hours and then, if you have an absorption problem, it is just a matter of time until it dwindles to nothing. Treating patients solely on the basis of serum levels isn't a good idea - if only because of c) above - and symptoms tend to be important ... but back to general state of knowledge of GPs.

Even if you don't have an absorption problem most of the B12 will actually go from your system quite quickly - so the drop back into normal range is what would be expected either way.

So, couple of things you could try:

i) seeing if taking some oral tablets helps get levels back up to somewhere where you feel okay - 50mcg tablets would probably work if you don't have an absorption problem.

ii) if that sort of dose doesn't seem to be working you could try higher dose oral/sublingual - these do work for some people as on average about 1% of your B12 is absorbed outside the ileum - doses of 1000mcg + a day - and there are plenty of places where you can source that doseage. There are sublingual sprays that you can get that some people find affective.

I personally supplement using nasal sprays - and some find that skin patches can work for them.

iii) trying to educate your GP, eg by writing to them to point out that dietary deficiency is unlikely and why ... listing your symptoms and referring to NICE and BCSH guidelines which both counsel against treating a B12 absorption problem on the basis of serum B12 levels - though it isn't as clear as it could be that this is what is intended - just that they refer to their being no point in testing further unless there is a suspicion that levels are low.

Going by symptoms in treating a B12 deficiency is fine - B12 isn't toxic though its a bit of a pain if you have a functional deficiency and have to keep your levels much higher than normal. In fact, given the problems with interpreting serum B12 it's probably the best way of monitoring.

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