many of us ME/CFS patients are on hydroxocobalamin, injectable, subcutaneous. ME/CFS doctors have been prescribing this for a long time now. KDM has many of his patients on 10,000 mcg 3x per week. i'm on less. recently i crashed, and stopped my b12 injections, just in case the high doses were contributing to too much detox and adding to my crash. over the years i have found that b12 shots give me more energy and stamina, but i personally have not found them helpful with brain fog. i do find B complex pills help me with irritability. i do not take magnesium, except a 250 mg pill at night, to help with sleep. i tried weekly magnesium shots many years ago. painful! and they did not help with any of my symptoms.