Just started on my MTHFR protocol last week. I started off at 1/2 tab for 6 days then upped to one whole tab. Since being on the regimine, I find that my usual fatigue is more profound. I feel almost zombie like and mildly depressed. My MTHFR ND says that starting on the B12 first is essential, before adding in the Methylfolate, so I am not on the MF yet. I also started back on Vit. D and probiotics. Maybe my tiredness and depression is a healing crisis from the probiotics, as I've also had some off and on increase in muscle and joint pain, which happens when I get a herx from various supps, and which also has also happened in the past when resuming probiotics. I am Hetero for MTHFR, and I have 19 other sub mutations, i.e. CBS, etc.. My levels for B12 are moderately low and for folic acid, extremely low. That being said, I would say that overall I think my heart palps and racing are noticably less. This has been a huge problem for me over the years. They certainly are not gone, but improved. I have also been having a ton of anxiety attacks and vagus nerve like reactions and I think that has improved slightly as well, since starting the Methylcobalamin. Also not having the usual side effects I've had when I've taken regular B12 in the past (could not tolerate it at all), so I am glad that I am tolerating the methyl version so well. Can starting up the Methylcobalmin being causing the increased fatigue, or is most likely the probiotics? Thanks.