@gracee41
In my experience (which may not work for others) the problem with methyl-B12 and methyl-folate is simply to start low, even super low and be patient.
E.g. even 50mcg of both would be good if they don't cause any harm. Then you can raise the dosage with time. It took me two years to be able to take moderately high doses of both.
Other forms such as Hydroxy-B12 didn't do much for me. When I tried substituting methyl-B12 for Hydroxy-B12 for 10 days I felt my energies fade away and lack of motivation and mental fog returning. It seems many others have experienced similar issues. People like Freddd in a very dramatic way, not my case.
As I said... a bit of experimentation is necessary, we're all different, but I can attest the superiority of methyl-B12 over the other forms. If you can also put some Adeno-B12 with the Methyl-B12 even better. Adeno-B12 usually is well tolerated by everyone.