Hi guys, I have A1298C ++, and I was advised by my doc to take methylfolate, mb12 and hb12. So I started taking the hb12 in smaller doses, and boy did I feel a difference......a NEGATIVE IMPACT -> it made me down in the dumps for a few days. I tried this 3 times over the next couple weeks, with the same result. Does anyone know why I could be getting this reaction? I don't have the guts to move onto methylfolate and mb12 as I'm worried I won't be able to cope at work.. I have high serotonin in urine, and blood. As well as high histamine in my blood. According to my 23andme results I have the following +/+ in addition to the MTHFR A1298C: DHFR CC +/+ GAD1 TT +/+ GAD1 GG +/+ MTHFD1 C105T CC +/+ MTHFR AA +/+ MTHFR TT +/+ MTHFR GG +/+ MTHFS CC +/+ MTRR GG +/+ As well as MAO-A R297R T + . Could this explain my high levels of serotonin? Many of the specialists and GP's I've seen were stuck as to why I have high levels.... Any comments would be greatly appreciated because I'm stuck myself as to what to do next... Thank you.