I am still testing but I seem to be sensitive to B12. Here is my recent history...... I started Enzymatic Therapy B12 1000 mid-December 2016 along with Solgar Folate. I started on 400 Folate but got really agitated. Cut the Folate in ¼’s and slowly worked up to 400 over time. January 10 and 18, I got a spasm / throb / pulling in the bend of my neck under my jaw. It is underneath where the salivary glands are. It is like I have a TENS unit stimulating the muscle to contract over and over in a very small spot. I haven’t had this problem for years and never figured out what caused it. By the end of January it was happening daily. I have no other symptoms with this. At times when it’s pulling, it happens every 15 seconds. Some days there is no spasm, just a slight tenderness in the spot but enough to be really annoying! End of February I changed to the Country Life Methyl B12 5000 (taking just 1/4 pill) because I didn’t want the sugar next to my teeth daily. I also started the Source Naturals Dibencozide. March 9, I saw an ENT and he saw/felt nothing. He gave me a 5 day rx for Prednisone. Day 5 of the Prednisone I had the spasm. It has continued off and on, some days more painful and annoying than others. March 23, I stopped the two forms of B12 and the Folate. March 26, the spasm had stopped. I had no spasm for three days so I decided to test the Methyl B12 alone. March 28 I took a ¼ pill (1250) in the PM then again March 29 AM. Just one hour after the morning dose I felt one quick yank. Nothing since but I haven’t resumed any pills. I will wait a few days and test the other two supplements to see what happens. I really want to take some form of B’s! After just two weeks using the B12 the skin on my fingertips and hands were so much softer with hardly any skin splitting on my fingertips. I also seem to sleep better. Last labs in December my B12 was 825 but I understand that isn’t the whole picture of the active amount. I appreciate any input or thoughts.