heres my story I have come to the conclusion that I am definately b12 deficient after reading up my symptoms primarily mental fog lack of attention and feeling weak old and tired before my time. I have been to the dr several times trying to figure things out and each time they check my blood and tell me I'm fine but deep down I knew something was getting missed and I've suspected it was a b12 deficiency for some time but everytime they checked my b12 it was fine but I am now thinking that was because I would take a b12 vitamin every once in a while and if I remember right I would take it before they checked my b12 and I think that might of threw off the tests. My symptoms have been getting worse to the point where I felt there was not much left in the tank I did take a b12 the other day and the migraine I've been suffering drastically subsided which led me to do some internet research and the jigsaw puzzle has finally fallen into place. The reason I feel like it took awhile to figure this out is because I thought my mental fog was due to hypothyroidism and my headaches were due to allergies but that seems to not be the case.The question I have is what would be the best road to recovery when I take a 250mcg b12 it seemed to help alot but when I took a 2500mcg b12 it actually made my migraine turn into the mother of all migraines to the point I felt my brain was swelling up and my eyes hurt and it actually made me go to the hospital where they did a brain mri and blood work and said all is well. So my question is could I be so low in b12 that when I take a high amount its too much for my brain to handle because thats what it seemed like the 2500mcg was sublingual and the 250mcg was not I've also suspected when I take medications my digest system absorbs them and makes them feel stronger than they should. Right now my stress level is really high and my morale and faith in dr's is really low specially after reading what being low in b12 can do to you and I need my concentration back and this migraine gone just thinking hard hurts. I have been reading b12 injections should be the way to go problem is getting a dr to listen to me and get them to prescribe it to me and has anyone heard of bad side effects from them? Can someone please give me some advice on what road of action I should take this migraine and weakness has been taking a toll on me I am really looking forward to a response of some good advice thanks.