Weak legs

I have I recently been diagnosed with b12 deficiency and have had 4 weekly doses and am due next dose end dec.i am due next week to see if levels have improved. However this week I noticed that I have no strength in my legs. This became very apparent this week whilst at work when I had to run very briefly. Legs felt like jelly for good couple of hours remained sore in thighs for the rest of the day. That night got several bouts of cramping in feet and calf. The same happened the next night. Now my calves hurt to walk but not at rest. Cramping has been more frequent since finishing loading doses. Should i be looking for other causes for this weakness?Any advise welcome.

20 Replies

  • Hii.. I hv also weak leg symptom due to b12.low

    . I feel i m nt able to stand for long Tim.. When i stand for 20 minuts my legs start shaking jelly legs i feel.. In outside i feel my legs ar nt stable..

  • Thank you for your response.

  • Hi Swainy

    It is not uncommon for some symptoms to appear to get worse before they get better as the B12 starts repairing the damage done to your nervous system and your brain starts getting multiple messages from part of the body it had "forgotten about" or lost contact with.

    I sometimes liken it to a badly tuned radio on which you have turned the volume up high trying to catch the programme you want when all of a sudden the signal comes in loud and clear and the blast nearly deafens you.

    A lot will depend on the severity and longevity of your B12 deficiency as to how long before there is no further improvement or recovery. Some symptoms will "disappear" quite quickly whereas others may take months or even years. There is no set timescale as we are all different.

    It is also important that your Folate level is monitored as this is essential to process the B12.

    There is a complex interaction between folic acid, vitamin B12 and iron. A deficiency of one may be "masked" by excess of another so the three must always be in balance.

    Symptoms of a folate deficiency can include:

    symptoms related to anaemia

    reduced sense of taste


    numbness and tingling in the feet and hands

    muscle weakness


    Folic acid works closely with vitamin B12 in making red blood cells and helps iron function properly in the body.

    I am not a medically trained person but I've had P.A. (a form of B12 deficiency) for more than 45 years.

    I wish you well

  • Thank you for your response. My folate is low also which is hard to believe as I love my greens. My gp has not said anything about my folic acid though nor has he said anything about why my b12 was sitting at 128. I didn't have any cramping before I was diagnosed. My gp just said that this was going to be a long term thing. Is there any other testing you could advise to get better picture of my current health as I am really struggling with this and don't know how I am going to cope until after Christmas before my next dose? ANY advise would be gratefully received.

  • Given that you are vegetarian your low Folate suggests that you have an absorption problem with your stomach and as your doctor accepts that your B12 deficiency is "going to be a long term thing" in view of your neurological symptoms I think you need him/her to either give you more frequent injections or supplement it yourself.

    I'm not qualified to give you advice but personally I use a B12 spray every day and I also supplement with a 400ug folic acid tablet each day.

  • You may not be getting enough B12 to repair the damage.

    I've had problems with walking too, when I first had what I now realise was probably B12 deficiency, I couldn't walk upstairs, I had to crawl.

    Recently (years later) during the course of B12 treatment my legs 'stopped working' - is the only way I can describe it - yes, I was able to walk but every step was a tremendous struggle. At the moment it's improved dramatically but I don't know why. I'm hoping it was all part of the recovery process.

  • weak legs has been one of my major symptoms and one that really infuriates me as I'm an outdoor type person and like nothing better than to go hiking. I can't manage the hills these days and have to stick to low level walks. even at that I can't do long walks. Going uphill can be tricky and my legs get very sore and weak. I had my legs scanned for blood flow and that was fine and also had my nerves tested shortly after I was diagnosed with the B12 deficiency and the results were fine too. I also can't stand for long periods of time as my legs get sore and I need to sit down. I do a lot of presenting where I have to stand and that can be problematic. The fact that this illness has impacted on things that I really enjoying doing gets me down. The GP referred me to neurology and I was also referred to the vascular clinic to get these things checked out so maybe worth asking your GP so that they can rule out other things. Hope this helps.

  • I know the feeling. I'm on my feet most of the day at work and I find myself grabbing a seat or perch wherever I can.

  • Hi Swainy, perhaps your potassium levels have dropped since loading doses. Eating plenty of potassium rich foods, bananas, kiwi, avocado mango, lots more may help. Also I started taking magnesium maleate a few months ago for excruciating cramps and they have helped a lot. Hope you feel better soon. Best regards.

  • Thank you for your advise I will look into the potassium further.

  • Do you know if you had macrocytosis - larger rounder red blood cells - if so then there is a possibility that your potassium levels may have dropped. Please speak to your GP/pharmacist about this as you can overdose on potassium but looking at some potassium rich foods for a while would probably help.

    If you have low B12 and are on injections that means that you have an absorption problem - probably PA and because this can also reduce your stomach acidity it will result in other mineral and vitamin deficiencies even if you have a good diet.

  • This is so interesting to hear about others having leg weakness. My situation is a little different because I'm battling bone tumors which I recently lost my right leg. Before that, I would try to walk in my cast and found I had to stop because my legs went weak. Such an odd feeling. I thought it was due to my back being off kilter so long on crutches. Now knowing I have PA and hearing about others with leg weakness and cramping, I wonder how long my b12 was bottomed out before they found the PA?!?! More puzzle pieces coming together

  • Thanks for your response. My gp was doing routine blood checked as I was having pains in bones and muscles. My level this time was 128. I did find out that a test I had done 5 years ago had my levels at 145 but that was not acted on do looks like I've had this issue with b12 for sometime. Thank God for my new gp at least he has acted on my results.

  • Low VitD can be the cause of painful bones and muscles. If in the UK the level suggested would be around 100 - in the US and other countries around 60 for optimal health :-)



  • I know that the size was about 13.5 which I believe is right near the top end of normal but gp didn't say anything about it so I assumed that i dont need to worry. Can gp test for potassium and other minerals that might be lower than normal. Only want to supplement those thst i need to.

  • suggest you discuss with your GP.

  • Thanks

  • Many people are low in Magnesium - you could read up on it as there are many types and some should be avoided :-) Taken at night is best I have read as it relaxes the body and hopefully your muscles.

    Do you know your Ferritin levels - if low in range ( under halfway ) then it could be prudent to have a Full Iron Profile done as low Iron can also cause weakness ( low oxygen supplies )

    Am also wondering with low levels of B12 and folate - how your thyroid is functioning and if it has been correctly tested ....

    Happy to help thyroiduk.org

  • No one has said anything about my magnesium being low. My bloodwork was b12 92(very low)instrinic factor 98(very high) folate low, MCV, always high(6 years now) RBC, always low, WBC high end normal range, MTHFR double gene mutation and now lymp absolute is high. I did the loading shots and took iron and doing weekly shots which has kept My b12 steady. My doc is switching me to daily sublingal methyb12 with folinic.

  • Thank you for your response. I haven't had any testing on thyriod. Gp was just running base long mot as he called it as I have had a lot of bone/muscle pains.

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