So I know that there are a lot of reasons to take the reduced forms of folic acid like folinic acid or methylfolate. However, I am not sure if this is a good idea for me. My responses below High dosage folic acid 4000mcg per day: Pros:My crash threshold is raised greatly for my body. I can even go on short jogs without feeling muscle weakness or air hung or anxiety symptoms. I can drink alcohol without any worsening of symptoms the next day. I get great sleep every single night. Cons:However, I get brain fog and brain inflammation symptoms very easily from exertion. The worst part is that I feel in a fog all day 24/7, and I don't want to talk to people at all. I also feel somewhat devoid of emotion. I mostly feel a constant strong sense of inflammation in my brain, even worse than the day after having a concussion in the past. No folic acid, just hydroxy b12 and 200mcg methylfolate: Pros: Brain is clear, almost no inflammation, unless I am active the whole day. I can talk to people and interact and joke just as quickly as they can. Basically, I feel like I have my personality back. Cons: My crash threshold is considerably worse. I get anxious easily, I get air hunger easier. I even get muscle weakness and muscle pains if I push too hard. Leading up to the last couple days I was on the no folic acid regimen and I crashed terribly. I was really scared and knew I hated folic acid brain fog, but remembered how good my body was on it so I had no choice but to go back to it. Well, within 24 hours I was sleeping like a baby for the first time in a month and my muscle weakness and pain that I had the last 2 weeks went away as well. A dramatic reaction. Thoughts: I think this is a clear sign of some sort of brain infection or neurological disease, definitely a sign of mitochondrial disorder and energy producing problems. Folic acid is supposed to be good for nervous system function, which it obvious helps me immensely. But why does it cause such horrible brain fog? Do I maybe not even have cfs/me but some sort of bacterial brain infection as an underlying cause? Maybe lyme disease? Moving forward I have no choice but to take folic acid, but will try to find the right balance of dosage that gives me a decent crash threshold, but still keeps the inflammation in my brain low enough where I can keep up cognitively with a conversation with people.