I had bad fatigue and brain fog on and off when taking MB12, Mfolate and minute does of ADB12. I also took potassium. I noted that my blood pressure was around 91/67 which is low, I normally have low blood pressure at around 105/70. I think this is due to potassium that I was taking (only 200mg). For me, if I have fatigue its normally due to lower than normal blood pressure. I have stopped for a few days and now have started again, with 250mcg mb12 and 200mcg mfolate and multivitamin, fatige ok, but also feel quite sleepy after mb12. Will this pass?