My MMA and Serum tests were skewed because as MrsD said, I did not stop taking B supplements before the test, as at that time I did not know I should, and therefore the serum was useless to me. The MMA came in at the low end of normal.

I did not bother with any further testing, as I just started on 5,000 (mcg or mg? one of them) of the B12 and since it is helping me, I continue to take it and B12 toxicity is rare.