B12 sometimes gives me headaches, but I think it's because it causes my heart to race, which leads to shortness of breath, which leads to me gasping a little, and then the headache starts because I'm trying to suck in too much oxygen. (I have to say, I used ONLY Jarrow B12 about a year ago before stumbling on this forum, and although it took about a month until I began having the shortness of breath and racing heart that I'm guessing is due to either potassium or magnesium, it made all of my muscle pain and neuropathy symptoms disappear. They came back after I stopped it. So... I know it's not the B12 of choice anymore, but for some reason, it worked for me AFTER it was supposed to be no good due to a formula change). I try to take enough potassium to stop these symptoms, but I'm currently finding it impossible unless I want to end up with a very upset stomach. I've stopped swallowing my pills - I'm breaking them apart and dumping the potassium powder into my drink instead. We'll see if that makes any difference. Does anyone know if B12 can cause a stuffy nose? Because I feel like it is, for me, but it's not a side effect I've really heard of. Kinda odd... Also curious if anyone else seems to have trouble tolerating methylfolate, and if so, what you ended up doing. I bought some Solgar folate, and when I tried both small and large doses (some people say start the big dose right away, others say increase slowly) I had a really big increase in muscle pain. I stopped cold-turkey, but I'm starting to wonder if I should give it another go since everyone says it's so crucial. I remember reading somewhere, though, that if you try taking folate before you get pre-existing inflammation under control, it can make it worse.