I have been discussing side effects of B12's, order to start B12/methylfolate, what and which form is best, and why do some have side-effects when others don't. Ben Lynch discusses these issues- esp. between 10-17 minutes in this video. He says Methylfolate does NOT mask B12 deficiency and that the safest way for CFS patients to start is B12 and methylfolate together. He also discusses why this doesn't work for some patients and why. He thinks adB12 might be the best choice with patients with mitochondria dysfunction. I wish this guy were my doctor!!!