Julia, I had leg cramps as well as burning feet and legs for the first month after starting methyl-b12 sublingual. I saw 3 of my docs for this, all of which said the cause was my feeling nerves regenerating. They also said to increase my potassium because this process requires more potassium than I normally needed.

Without much b12 coursing around, doing it's thing, building, repairing, allowing simple body functions possible, things most take for granted, our body just don't use much of the good nutrition we eat. B12 is a key that allows everything else to work properly. Put in that key and wham, things we've long forgotten, start happening again. In my case, a life altering surgery left me with little b12. Many of the changes I experienced during recovery were not just due to healing, but due to a b12 deficiency. I was grateful to be alive, the changes were assumed to be caused by the surgery.
Until that first dose of methylcobalamin I hadn't yawned, coughed, or been able to stretch my muscles. I "miraculously" was relieved of all allergies. (no b12=no immune system. Allergies are due to an over-active immune response.) Fibroids and psoriasis was gone
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Many of my psoriasis friends are on biologic injections to supress their immune sytem. In essence, this is what my b12 deficiency did to/for me. With that first dose, everything changed, some not so good, but certainly wouldn't give up my memory and pain relief I've experienced.

Within a month of treatment, burning pain was gone, leg cramps still occur on a day when I take more b12 than usual. I eat a banana or a sweet potato and all is well. I've found rebuilding b12 to be very uncomfortable. The leg cramps are the worse pain I've ever expeienced.

I've had to stop using b12 several times in 8 months. Each time I stop, numbness and pain returns, as well as digestive problems, but allergies subside, no coughing, sinus, etc...As soon as I restart, leg cramps restart, though not as bad, I increase my potassium and all goes back to my somewhat normal function.

I use Pure Encapsulations liquid Methylcobalamin 5000mcg. I only use a small dose of this each day. I have never experienced mouth sores from it. This can be found online as well as some pharmacies. This is the brand recommended by all of my doctors. Perhaps a switch in brands would be helpful. I would also check with his doc to get their take on the mouth sores.

Hope some of this helps you all and best luck.

deb...