I understand that methylcobalamin is absolutely life-giving to many. However, some people do have severe adverse effects and I hope to discuss that here. Hopefully we can avoid getting unnecessarily worse!
I was originally given very high daily doses of methylfolate (1000mcg) and methylcobalamin (5000mcg) sublingual for 4 months and had a number of severe reactions both physical and psychiatric that landed me in the ER.
I didn't understand the effects at the time, and I'm not sure why I responded this way. I suspect it has something to do with genetics. I am not sure if I will ever tolerate the methyl form.
I stopped due to the adverse effects and immediately developed the clear neurological signs of B12 deficiency, even worse than before.
My Dr gives me cyanocobalamin now, but that helps very little with my neuropathy and quickly wears off. I supplemented 1000mcg methyl once every other week for three weeks, and the neuropathy has responded considerably. However, even that small amount of methyl is excruciating- palpitations, diarrhea, cystic acne, burning skin, severe anxiety. They last for weeks after the dose.
As a commenter said on another forum, "I feel like my brain is being microwaved!" The psychiatric side effects rival that of B12 deficiency, so it's quite a pickle to be in.
As MTHFR treatments become more popular, I'm reading more stories like mine. Often the side effects were not expected. Clearly, methylcobalamin is not without side effects for some people.
If you had adverse reactions to methyl, did they go away? Did you acclimate? Do you tolerate other forms? Do they help with neuropathy?
I'm not trying to discourage anyone from taking methylcobalamin since I know it helps so many, just trying to get the side effects on the radar