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I'd like some advice on a health issue which could relate to B12 deficiency.

Recently I started experiencing occasional numbness mostly in the legs and feet but occasionally in the arm/hand. I thought it might be due to sitting too long in one position and thought little of it. This escalated over the summer especially at night which in turn created a sleep problem. I found it was becoming every night and sometimes also during the day for a while so thought I should go to the doctor. Before doing so I looked online for some possible explanations and came across lots of information on B12 deficiency. This possibility seemed plausible to me since although I am not vegetarian, I am only an occasional meat/fish eater. Some other symptoms mentioned coincided, such as hair loss (slight) and greying, increased frequency and urgency to pee, one night I also suffered extreme dizziness which I put down to getting out of bed quickly but could also be related. When I went to the doctor I mentioned the problems and the info I had seen about B12 deficiency. He ordered a blood test but since it couldn't be immediate due to holiday commitments we agreed I should start a B12 supplement to see the effects. I started with Solgar B12 1000 micrograms once or twice a day. By the end of my holiday (10 days) the numbness at night had decreased massively and I only experienced it from time to time. Since returning I have experienced no problems at all. The blood test was done on my return (10 days after starting the B12 supplement) and the results came back with no B12 deficiency (890 pg/mL). Of course it's impossible to know what the initial levels were and the effects seem significant to me. My folic acid was slightly low (4.3 ng/mL) so the doctor told me to continue with ONE B12 a day plus a folic acid supplement of 10 mg a day. After taking the first folic acid tablet, that very night, the symptoms of numbness in the legs/feet and sleeplessness at night returned. I also noticed that the leaflet inside advises against taking it with B12 deficiency because it may increase the need for the B12 and aggravate neurological symptoms. Clearly I am not going to take the folic acid (which also seems a very high dosage based on what I've read) again but what should I do now? The doctor said I should return in 2-3 months for another blood test (after having taken the folic acid during that time) but should I return straight away to tell him of the effects of the folic acid or wait whilst continuing with just the B12 once a day? My main worry is that the diagnosis is not clear and whilst I hope it’s merely a problem of low B12 in my diet easily corrected by supplementation, I am concerned that there is an underlying problem that is hard to get at.

Of course after such a short time on B12 I presume I could just come off for a couple of weeks and retest? BUT I don’t want the numbness etc to return obviously and would prefer a different solution. Other abnormal results in the blood test were: eosinophils 9.1%/0.51 in the count, basophils 0.5%/0.03 in the count, HDL cholesterol 79 mg/dL (the doctor said this was good!), triclycerides 64 mg/dL.

What would you advise? Does this sound like a simple B12 deficiency? Could it be PA?

By the way, I am a British citizen currently residing in Spain and the doctor visits have all been carried out in Spain.

Thanks for your help.

11 Replies

The advice on the packet re folic acid and B12 is a bit misleading. Your body needs both folate to be able to process and use B12 effectively. There are a few symptoms of a B12 deficiency that can be masked by high levels of folate and if treatment of a B12 deficiency at the time is left untreated because the concentration is on folate then the neurological symptoms from the B12 deficiency will just get worse and could become irreversible.

However, you are being treated for the B12 deficiency and you need to get your folate levels up.

It may be that folic acid isn't the right form for you - folate from food is the best form so if the problem can be resolved by upping folate rich foods then that is ideal.

However, there are also a number of genetic mutations that can interfere with the bodies ability to methylated B9 (folate) ie process it into the format used at the cell level. It may be that you have one of these genes and that is interfering with everything. A different form of supplement may help - but it depends on the genetic variant involved and different forms could actually make things worse

Condition is called MTHFR and this seems to me to be a good introduction to it

This paper is quite a good summary of problems with taking various vitamins so may be worth looking in detail at the section on folate (B9)

There have been some reviews of the recommendations since it was published but the underlying recommendation hasn't changed as far as I am aware.

Also bear in mind that the problem with B12 may not be just diet - the doses you are being given are very high (600x RDA) and are doses that can be effective in correction a malabsorption problem in some people (but not everyone)


Thanks for this detailed information. I've had a look and it looks like there are indeed more risks with high levels of folate supplementation than with B12 which has no indications of problems at all. It also reiterates that folic acid can aggravate or exacerbate neurological problems in patients with PA. To explain, I've been taking the high-dose B12 because I suspected I had a problem with B12 and wanted to see if the supplement would help quickly. Actually it really seemed to help a lot and I really thought I'd done a good bit of self-diagnosis ;-) The setback came the day I took just one folic acid 10mg tablet so I thought it couldn't be a coincidence, right? Now I've gone back to just the B12 supplements but there's still a bit of leftover numbness and achiness in my leg. I'm hoping this will go soon. My problem is how to get a confirmed diagnosis without quitting the B12 supplements (I'm happy to reduce if it goes back to normal again but I don't want to suffer the symptoms I had again which were getting gradually more frequent and worse)...


One more thing I forgot to mention... looking at different information last night I saw many sites which indicate the 'normal range' for folic acid levels to be 2-20 or 2.7-17 ng/mL NOT 4.6-18.7 as it said on my blood results sheet. I'm not sure how there is such a discrepancy but that would mean that at 4.3 my levels are fine and certainly with a bit of effort on increasing folates in my diet that shouldn't be a concern, right?


The only range which you should ever use for interpreting blood test results is that of the lab which did the test.

We never know quite why the ranges vary and it could be to do with the technology used. If you see ranges that are a bit different, it might legitimately raise a question in your mind, but you cannot sensibly use them.

(I am all too well aware that we can see medics around the world using their local ranges with results from patients tested eslewhere. And writing "guidelines" that make no allowance for such varying ranges. Just because they do so does not mean they are right or that we should follow their bad examples.)

This is one fairly typical statement for a folate test:

Adults: 2-20 ng/mL, or 4.5-45.3 nmol/L

In your original post, you wrote:

My folic acid was slightly low (4.3 ng/mL)

In the reponse I am replying to you wrote:

2-20 or 2.7-17 ng/mL

And the first quote in this response implies that 2 ng/mL is the same as 4.5 nmol/L. I'd suggest that with those numbers being fairly close numbers plus two different units being used, there is plenty of scope for mistakes and confusion.

Regardless, being at the bottom of the range is not as worrying as being miles below - but probably not the optimum place.


Its difficult enough to get a proper diagnosis of B12 deficiency without supplementation - and more or less impossible once supplementation has started unless you stop for a considerable length of time - 3 to 5 months - which it sounds like you aren't prepared to do and I don't blame you.

Sorry that I can't be more possitive.


I don't really understand why if the body can't store B12 which is why you need to get it from somewhere else on a daily basis, it would take so long after stopping supplementation to be sure that you could get an accurate blood test done. Am I missing something??


99% of B12 is absorbed in the ileum. It then goes into your blood. If you have excess then your body will store it in your liver and then release it in bile back into the ileum for re-absorption into the blood when it is needed.

If you have an absorption problem then this mechanism breaks down.

However, when you supplement you still have large amounts of B12 going into your blood. If this isn't filtered out by the liver for storage then it is filtered out by the kidneys and passes out of the body in urine. This process depends on the relative concentrations of B12 - high concentrations of B12 and it will be filtered out quickly - lower and it is filtered out much slower.

The result is that if you have an absorption problem but have supplemented the B12 is likely to stay around in your blood for a long time - hence the need to stop supplementing.

Also the supplementation may allow the liver to start storing and releasing B12 again. Whilst this won't be as efficient as a person without an absorption problem it can take a month or two for the body to slowly release any reserves the liver has built up. In a normal person the amounts stored in the liver are very significant and can be enough to keep some people going for years or even decades.

Because doctors are so fixated on normal levels rather than looking at clinical symptoms it can take a long time for levels to fall to levels where they are either bouncing around the low end or off the scale and recognised as low.

Basically the problem is the method of testing - which doesn't really bear any relationship to the absorption problem (just uses a rather hit and miss secondary indicator) ... and also doesn't look at what is happening at the cellular level.


OK, I see what you're saying. Is it the same problem with the other tests I've read about: MMA, HoloTc, Homocysteine? Or would a doctor be able to spot absorption issues through these even with continued supplementation?


HoloTC is looking at another form of B12 - so is going to be the same issue.

Unlikely that doctors would look at MMA or homocysteine without B12 already being raised as an issue, and the fact that your body will have some B12 to use may have affected both levels anyway.


Hmm, catch 22...


"The body needs ample B12 in order for folate to work and one of folate's crucial jobs is to synthesise the nucleotide 'building blocks' of DNA. When folate is trapped in an unusable form due to lack of B12, it can't do this job correctly".

Here are more links which might help: - page 17 - the best treatment for B12 def. is vitamin B12 without additional folic acid. (an excellent film on this site with info that folic acid should never be taken while B12 low, as it can precipitate or worsen neurological symptoms).


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