I'm not sure what the answer is, but for what it's worth I have this too. I would suspect it's not from trying the glutathione, since that wouldn't line up with my experiences (mine was like this before I knew what glutathione was
). The levels weren't elevated before crashing out badly, so there must be something going on.
My B12 and folate test very high (like you, I supplement these), but there are also indications that my body is maybe not actually able to USE what's there, so that could be it. Or maybe that the genetic issues in my body mean I need even more than the crazy levels of B12 I take daily.
There is also some possibility of hypothyroid issues because of my free T3 level being a bit on the lower side, but the standard thyroid tests don't turn up anything, and my heart rate is certainly not slow.
I'm pretty sure I have a low blood volume issue, and am pretty chronically thirsty. So dehydration could be a factor.
I haven't looked into copper deficiency (though I actually just had that level tested, so now I'm interested to see what comes back), but I eat a ton of cashews and some other copper-rich foods. I do get VERY dizzy with much lower levels of zinc than I'm supposed to, though, so I have wondered if there was something up there. I hadn't heard the copper and MCV/MCH connection before. Thanks for mentioning it,
Crux.
Sorry I'm not more help, but I'm glad you asked the question, and am interested in what other people have to say. I would like to get to the bottom of this abnormality too!