I have this and so does my adult son. For my case and his, our diet had to change big time. I also have had my thyroid removed and parathyroid many years ago as it was so unstable. Synthroid ever since so I could check that box off. The covid shots through my body into a mess, and my son and I both had huge reactions. MTHFR was mentioned to both of us in two different states. We both ended up with holistic medicine doctors to deal with Mast Cell Activation and the supplements required to correct out chemistry . Their protocols were excellent. Take a look at Becky Campbell’s amazing site, and Beth O’Hara’s.. There are many sites around the entire world for MCAS . I use Becky’s supplements called Optimal Reset, and they are a Godsend for correcting . MTHFR is very good at causing weird upsets! I react to everything and have a long allergy list. My adult son actually went into anaphylactic shock from it after one of his covid shots. I was very sick after each shot. I hope you check out the web sites for MCAS and see if that has any ah ha moments for you! Good luck!

My b12 was over 2,000 but lab shows how much B12 in body, does not show how much is usable so test is not correct. I take daily b12 shots and not synthetic kind, has to be Methyl type. That's great your homosysteine is ok.