Nanc, I think there was a misunderstanding.

You said: I tried sublingial B and they gave me an instant bad headache.

I'll try to be more clear.

If you have the MTHFR mutation, cyanocobalamin shots are doing nothing for you. Your body can't use it. They are not HEALING your nerves and other tissues. B12 is stored in the liver. The cyano is probably being stored in your liver but not helping your tissues.

Cyano needs to be converted by the liver into methyl before it is "sent out" and is used by your body.

That's why I thought you could either have a MTHFR issue or your liver isn't converting cyano to methyl.

And that is why I wondered if the methyl B12 you took caused a headache, due to your body finally getting the B12 it needs to the tissues and causing healing, which can come across as pain.

Is that more clear? I hope so!

Annie