How much can folic acid alter the results of a B12 blood test?

My GP says that with a B12 test result of 444 I'm absolutely not suffering from B12 deficiency. But I have been on 25mg folic acid per week to help with the side effects of an RA immune supressant drug, Methotrexate. Over the past 4 weeks I have been getting severe peripheral neuropathy (pins and needles everywhere and numbness in my legs and feet). I decided to stop taking Methotrexate and now I've been told by my doctors that I wouldn't be allowed it again in case it has damaged, or would cause eventual damage to my peripheral nervous system.

I don't want to come off this drug permanently and risk my RA returning, only to find there was another cause and it's just gone undetected. I asked my GP about the possibility of folic acid compromising the B12 results but he knew nothing about this. The rheumatologist just said that it wouldn't neutralise such a healthy B12 result.

They are probably both right but I just wondered if anyone can tell me how much a large dose of folic acid could skew my B12 results and whether, if the neuropathy continues, it would be worth my while taking supplements anyway.

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19 Replies

  • Tilda,

    Taking folic acid does not directly affect your serum B12 result. What happens is it corrects any macrocytosis (enlarged red blood cells) so haematological changes of B12 deficiency are masked. This is a problem because a lot of doctors rely on the FBC to diagnose the condition, and only look for anaemia and macrocytosis. Many doctor's do not realise that neuro symptoms can be present in the absence of anaemia, or with a "normal" serum B12 result. This is called functional B12 deficiency, I think I've sent you articles about this before?

    I assume what you're really asking is can you be B12 deficient with a result of 444. The simple answer is yes, you can be deficient at any serum B12 level. It is not a sensitive enough test to know what's going on at tissue level, it simply measures what's floating around in your blood, both active and inactive forms of B12.

    Basically, this test is not sufficient on its own to rule out a deficiency, you would need to have active B12 and MMA tested as well to get a clearer picture. The easiest and cheapest option is for a doctor to just trial B12 treatment and see if you respond, but the chances of finding a doctor who will agree to this are inexplicably slim.

    H x

  • Oh Hampster I have read and tried my hardest to to take in the PDFs you have very kindly referred me to.

    The trouble is that I'm splitting my rather limited brain between completing a major public art project (lots of budgets and image files plus printing concepts to grapple with) and my health and my husband, three sons and two dogs. So its not going in properly (rather like my B12 absorption perhaps?)!

    My instincts tell me that something else is going on here but my GP and rheumatologist seem to have closed ranks, deciding perhaps that I'm becoming over anxious - in their paternalistic wisdom.

    I told a white lie and explained that I have a good friend with PA who had almost identical symptoms to mine and who has sent me PDFs about unidentified B12 deficiency. He just shrugged and made a rather visible mental note to himself (or to share with my rheumy) "oh heck she's onto thyroid/ anaemia stuff now!". He said because my MCV is within normal range still (just) and my serum B12 is so good and I am not anaemic there is no possibility that I'm B12 deficient.

    And despite peripheral neuropathy being listed as a very rare side effect of Methotrexate, all my doctors are convinced it is this now. If the neuropathy continues after the drug has flushed out (several more weeks) then they will say that unfortunately this drug appears to have caused more lasting damage to my peripheral nervous system and there's nothing they can do for me apart from even more scary RA drugs. The GP took my ANA and Rheumatoid Factor again at the rheumatologist's request and performed a rudimentary nerve and reflex test on my legs - which had him conclude that no damage to my central nervous system yet at least.

    By this time my RA might well have returned in the form of a great big flare which will require high dose steroids (which I don't handle well) to get back under control. So I really want to try and address this more intelligently than they seem able to do while I still can.

    If I give the drug a few weeks to clear fully and the neuropathy is still there then I'm going to assume it could be B12 issue and take my supplements whatever. But I do want to be methodical and see if the Methotrexate is in fact responsible or not so will stay away from B12 supplements until then.

    Thanks for confirming that I still should not be discounting the B12 issue yet and for putting up with my struggle to grasp all this stuff too!

    Tilda x

  • Trust me Tilda, you know more about this already than your hopeless doctors!!!

  • Ugh I can't help frothing at how paternalistic my man GP was on Tuesday. If I hadn't been so full of raging ants on fire!) and numbness in my legs and feet I would have been more confrontational I think. But then again, he appears so civilized and certain, and it's hard when you feel they are closing ranks but your future depends on them! Especially when the drug Methotrexate is involved and fearsome pain and even more scary drugs (anti-tnfs) seem to be the next thing to anticipate with dread! Thank goodness for people like you really. I'm so grateful. Tilda x

  • It sounds like you have Autoimmune problems , you may find synthetically sourced medications will cause reactions ,I have ADRs to almost every thing since being sensitised by "Human"G/M insulin in 1980 .

    I am in real trouble Levothyroxine causes crippling pain , I cannot tollerate synthetic bone density drugs , have to use Vit K2 , can only tollerate Almus Enalerpril and Doxazosine amongst the host of blood pressure medications I have tried ,Steroids and Nsaids are a no . Thanks to IDDT can still get my Bovine Insulin , NovoNordisk tried to have it taken off the market .

    Do your research and find a solution by trial and error the NHS wont help , you will have to be confident and fight your corner ,Best Of Luck , I`ve been there and got the T shirt

  • Thanks John. I emailed my GP and asked him why he had taken my ANA and Rheumatoid Factor again and he said that the rheumy had requested this to check for any crossover autoantibodies. I think he might be thinking of Sjogrens. I'm wondering about Vasculitis and PA still but just waiting to see if the prickling and numbness leave my body as the Methotrexate wears off. It is definitely all part of the autoimmune state with me because I have Hashimoto's too but I've taken Levothyroxine for many years now and it never seems to have done me too much harm. But as you rightly say the whole meds issue is like a never ending house of cards that keeps getting built and then collapsing as another element comes in to play. Methotrexate is a cytotoxic chemo drug given to people with various autoimmune conditions from RA to Lupus to Crohns. It is a scary drug and I'm rather relieved not to be injecting it into my belly once a week anymore I admit. It didn't feel good at all. But then RA is a very scary disease too. Tilda x

  • It sounds like you have Autoimmune problems , you may find synthetically sourced medications will cause reactions ,I have ADRs to almost every thing since being sensitised by "Human"G/M insulin in 1980 .

    I am in real trouble Levothyroxine causes crippling pain , I cannot tollerate synthetic bone density drugs , have to use Vit K2 , can only tollerate Almus Enalerpril and Doxazosine amongst the host of blood pressure medications I have tried ,Steroids and Nsaids are a no . Thanks to IDDT can still get my Bovine Insulin , NovoNordisk tried to have it taken off the market .

    Do your research and find a solution by trial and error the NHS wont help , you will have to be confident and fight your corner ,Best Of Luck , I`ve been there and got the T shirt

  • Hello again, I have wondered about Sjogrens , first heared about it on the Quinalone Toxicitacy web site . I was badly effected after being given 3 bags /day for 4 days of Ciprofloxacin for an ear infection , then later in a link about Dr Hashimoto who also noted it in his Thyroid research in about 1930. There are tests by taking deep muscle cores , but as there is no treatment and risk of MRSA it is futile , but it does fit with the Polyglandular Autoimmune damage to 5 Glands diagnosis I had to pay for in 2006 caused by Human Insulin .

    Part of its operation is to attack internal organs , P/A , Thyroid ,Pancreatic Insufficiency,( the cause of 229 insulin coma`s between 1980 and 2006 ) plus Adrenal that did recover , and by my TSH results my Pituatry

  • I think there is a big distinction between primary Sjogrens and secondary Sjogrens - the latter tends to be far less severe. All as well as its come about through other autoimmunity such as Lupus or RA. I'm not sure why, when it can have so serious an effect on people, so many have hardly heard of it. Same goes for Vasculitis which can be a secondary condition of RA - inflammation of the blood cells. And people think cancer is the worst disease we can get?

  • Hi Tilda T

    Hampster is quite correct re. your Serum reading of 444 not ruling out a B12 deficiency, there are records of people with much higher Serum levels than that, still being deficient. Personally may I suggest that if you have not already done so, then you might be well advised to seek an Intrinsic Factor Test, following that a Parietal Cell Antibody test both on the NHS, if these come back showing Negative, then may I suggest you ask your GP to submit a blood sample to Dr Dominic Harrington at Guy's / St Thomas Hospital in London and ask him to test your HoloTC levels. Should this prove to be inconclusive, then as Hampster so correctly states, you will need to have your MMA tested. THEN!!!! and only then in my opinion, can you be sure of your true B12 readings. Try ringing Denise Oblien on 0207 188 7188, she will advise you as to your best way forward and she will even put you in touch with Dominic if nessacery. You could do the HoloTC and MMA privately if your GP won't play ball and sadly that is very likely. The HoloTC will cost you £18 plus a posting pack which costs a further £12 ie £30 in total, plus the MMA if that is nessacery and it may not be, That will cost you a further £98 I believe. BUT! for a grand total of £128, you will have an answer.

    Hope you find a willing GP, but they are very thin on the ground. You could always ask to be referred to a local consultant, it worked for me. Best wishes B12 Turbo

  • Many thanks B12Turbo. What kind of a consultant would I ask to be referred to - an endocrinologist?

    I ask this more out of interest than out of any hope that either if the GPs in my practice would possibly refer me or take any of the above tests you suggest. But it is very useful to have this up my sleeve at least and if the neuropathy persists I will go down the private route.

    My GP says that my MCV is under 100 (97.8) so this confirms that my B12 is fine and isn't contributing to my peripheral neuropathy. He refused to entertain the idea that 25mg folic acid a week might be masking my B12 results. I am presently waiting to see if the neuropathy goes away as the methotrexate leaves my system.

    My rheumy consultant is not convinced that the Methotrexate was causing it but he too said, after conceding that folic can mask B12 deficiency at this high dose, a reading of 444 made this very unlikely.

    But as the neuropathy is listed as a very unlikely side effect of the drug too I am keeping my mind well and truly open. I think the neuropathy might be fading a tiny bit but it comes and goes and I'm on Amitriptyline which stops the worst excesses. At night my hands and feet are burning with the intense tingle and keeping me awake. So far the RA hasn't returned but if and when it does I know that pins and needles will be the last thing I notice.

    I do have B12 supplements and plan to start taking them in another 2 week's time, if the polyneuropathy continues. The other thing I wanted to ask you PA sufferers is whether a month of poly neuropathy ties in with anyone else's experiences of PA - wouldn't I have started to have trouble with my central nervous system by now as the neuropathy would be more progressive than mine appears be? This is what my GP said re MS too.

    Meanwhile I'm also reading up about Sjogrens and Ra Vasculitis. Tilda

  • Hi Tilda,

    B12 deficiency can cause rapid deterioration, but actually I think symptoms more commonly creep up very very slowly, such that you might not even notice them, or you just get used to them. I actually just had a question, I know you have regular FBCs, but do they actually test your folate levels to see if the supplement is getting through? Folate deficiency can cause numbness and tingling too.

    H x

  • No they don't test this Hampster. I asked him to last week but he said it wasn't worth it because I would only have a folate deficiency if I had a really poor diet - which I absolutely don't. He is very hard to argue with though and makes me feel like a health obsessive if I ask these kind of questions.

    If it carries on I will get really tough with him though because I think you are quite right and I am just getting really used to it - as I do to some extent with pain. I had this same pins and needles a whole year ago and it lasted for 3 weeks and they said it was active RA because my ESR was high. But my RA is still being quiet now and yet this burning neuropathy wakes me every night. X

  • I don't understand this doctor, he's giving you folic acid because your RA drug is a folate antagonist, but how does he know if he's giving you enough/too much/too little if he's not testing your folate? Am I being thick here? I would demand a test for serum folate, red cell folate, and homocysteine. Only then will you know if it's getting to tissue level. Will try and send you some good links; this makes me soooo cross!!!

  • Well the good thing is that I'm off the Methotrexate so also off the folic now too. At least I suppose that's good?

    I don't think he really adds the folic acid into the equation because it was the rheumy who upped my dose from 5mg to 20mg per week because I was getting so sick. He just signs the prescriptions.

    Everyone on the RA site takes around this amount or more of folic acid if they are on Methotrexate. But I do promise you this stuff about diet is what my GP said when I asked him about my folate levels a week ago. I am really trying to be firm with him and the woman GP. I think they are so focused on the RA and the MTX that they aren't really looking beyond it as I am trying to do! I won't be getting a regular FBC again now I'm off the MTX. X

  • This is interesting, compares taking folic acid versus leucovorin - folinic acid (a more active form). Suggests the more active form might reduce the effectiveness of the methotrexate, so maybe that's why they use bog standard folic acid:

    Still think you should ask your GP to actually test your folate levels, then you'll know where you stand. It's not an expensive test.

    H x

  • Many thanks H I will. I've read that RA Warrior blog before - she's great. My list of possible suspects for the pins and needles has just grown as an RA friend has gone on the RA HU and described word for word my neuropathy symptoms (burning soles, numb cold legs and pins and needles in hands and elbows) which she says for her is always a sign of increasingly active RA. I feel sure I have something sinister and systemic going on that if anything the lower dose of MTX was not quite holding off perhaps. I will storm the surgery next week when I'm back from a work trip - and tell him I want my folate levels checking and won't take no for an answer this time! Tilda x

  • Couple of Japanese studies done regarding Methyl B12 and RA:

    Quote: "Thus, methyl-B12 may become a potential agent that would be able to control the pathophysiology of RA."

    Quote: "These findings indicate that methyl B12 suppresses mainly the cytokine production of T lymphocytes."

    Not really sure what the second one means! but both seem to suggest that methylB12 would be a good addition for RA sufferers.

  • Brilliant research thanks Hampster! I will add these to the ever growing list of things I need to be aware of. Tilda x

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