Symptoms of b12 deficiency

Hi! I was put on metformin because of my pre diabetes. Two months later I developed severe leg cramps and twitching, my hands and legs are tingling. My doctor told me to take 1,000 mcg of b12. Well my cramps stopped but not the tingling and twitching. I don't think it's enough. She says I should see a neurologist because she "never heard of" this happening to anyone who was on metformin (even though she told me to take b12!). I think I have a severe deficiency. How much b12 should I take to alleviate these symptoms? P.S. I have an appointment with a neurologist.

17 Replies

  • B12 deficiency caused by an absorption problem - and metformin is one - tends to develop slowly - even over decades so may be that there is something else going on, or else you you were already quite low on B12 and taking the metformin has just accelerated an existing problems.

    Unfortunately the dose you are taking is going to make it quite difficult to clarify if there is an underlying/pre-existing absorption problem.

    First question is do you have any other symptoms and if so how long have you had these.


    B12 isn't toxic so there is no real limit to how much you can take.

    One possibility is that you may now be folate deficient - particularly if your folate levels before you started on the tablets were towards the lower end of normal range. symptoms of folate deficiency are pretty much the same as those of B12 deficiency because the two work together.

  • Thanks so much for your answer! I had no symptoms before going on metformin in end of February other than occasional toe cramps/Charley horse at night. Metformin was great - keeping my numbers down - I was very happy. Then in March my legs started feeling "funny". Then in April my calves started getting "tight" so I did a lot of stretching. Then in early May severe cramps! I I will look into the folate issue.

  • It seems strange to me Kwizna that your doctor has "never heard of" people taking Metformin developing a deficiency when it is clearly indicated on the leaflet enclosed with the tablets that they will cause "low levels of Vitamin B12 in the blood". It may have been that you were already low from previous blood tests and that's maybe why, your doctor knowing this, she recommended the supplements.

    Please do ask for your Folate to be tested for as Gambit62 says this and B12 helps your iron to make red blood cells among other things.

    I'm not a medically trained person but having had P.A. (a form of B12 deficiency) for 45 years and also on Metformin for Type 2 diabetes I am aware of the risk although I don't think it's applicable in my case as I have B12 injected.

    I wish you well

  • Ah! But do doctors ever read the Patient Information Leaflets?

    At best, they are likely to suggest you ask your pharmacist. After all, there are lots of medicines out there and doctors can't know about all of them.

  • Agreed helvella and suitably humbled

  • clivealive and helvella - given that the GP suggested B12 supplementation I'm sure they are aware of the link between metformin and B12 deficiency but sounds like they are surprised - as I am - at the rapidity of the onset of the problems and that only some have been resolved.

    May be that I am being overly generous but ...

  • Difficult to be sure - possibly the doctor understands that the symptoms could be due to low B12, but had not linked that to metformin?

  • I guess it may depend on how much Metformin was prescribed. I remember I was on a high dosage of 8 x 500mg every day when I started.

  • When I started metformin she said I should take a multi vitamin with b12 in it which I did. When I told her about the leg cramps she took me off and told me to take 1000 mcg of b12 but didn't tell me which kind to take. I am taking methylcobalamin drops.

  • metformin is the most common form taken orally - you can get hydroxo and cyano tablets/sublinguals in high strength as well.

    there are a few cases where people haven't been able to convert methyl to adenosyl (the other form that is used at the cell level) so it may be worth trying looking for some hydroxo/cyano high dose (as they can be converted to either methyl or adenosyl) and see if that works any better.

  • However, onset that rapidly is really unusual for B12 deficiency so quite possible that there is something else going on.

  • If you have a severe B12 deficiency, oral supplements will help but probably won't be enough. Your levels of B12 and vitamin D should be checked. I have ordered a spray form of B12 from Australia. It is supposed to have a very high absorption rate. Transdermal patches deliver more than oral tablets, as well. Look for methylcobalamin form of B12. If you test low, your doctor will probably prescribe replacement shots to bring your levels up.

  • I'm horrified that Metformin is prescribed for pre diabetes. Two friends (one, a nurse) were diagnosed with diabetes 2, and put on Metformin - they followed Dr Michael Moseley's, 'The Eight Week Blood Sugar Diet', and totally reversed their diabetes.

    GP insisted on Metformin still be continued for six months !

    PS I'm self injecting every other day for my own tingling tongue, fingers and toes Kwizna to prevent further damage

  • Me too. Similar thing happened to me. I went over, just, into type 2, and the Endo wanted to put me on Metformin. I asked to be retested as I had been doing the Michael mosely's plan for a couple of months since my last test. Sure enough levels had come right down. The medical report said high risk of hypoglycaemia if on medication. I know of the connection between Metformin and b12 so wanted to avoid it for as long as possible.

  • That's great Daisy - so good to know that there is an effective harmless alternative to just resorting to a drug as a cure all, that, in the end, is not 😟

  • I agree! I would rather spend my money on nice food and supplements than line Big Pharma's pockets 😋

  • 👍

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