Yeah, I've heard Rich say that adb12 can convert to mb12 too, but if it's true what adreno said about adb12 staying in the body a lot longer could that still be a problem? Hopefully, he'll weigh in on this subject. I haven't been able to locate much information about a ratio although I haven't dug very deep. If there isn't a problem with them being unbalanced then that might give people who can't tolerate methylcobalamin, but do ok with adenosylcobalamin an additional option. I'm not saying in place of hydroxocobalamin, but it might be helpful as an add on since adb12 has different functions than mb12 and some people might need more than just what comes from hb12. Most of the talk here is about methylcobalamin, which I get because that's what's needed for methylation (whether taken directly or converted from hydroxocobalamin) so I wonder how much the talk about some sort of a ratio is just theoretical. I suppose it never hurts to be cautious. My dad who's only taking adb12 has MCS. While I don't want him doing methylation, I think taking B12 would be helpful for him. Even though my dad has MCS and is in his late 60s he still works full time. It helps a lot that he's an artist so he works at home and is thus able to limit his exposure. There's no way that he'd be able to work in an office. Even now, after he's made a very gradual recovery over the past 10 years working in an office would not be a possibility. Although working as an artist might seem easy, he does work very hard and he can't be dealing with monitoring his potassium all the time. Especially since some of his main symptoms are fatigue, sleepiness, and mind fog he might not realize if he has low potassium.