My dr suggested giving me a b12 shot when I mentioned my b level was slightly low at 300 a while back without checking my blood levels which was actually at 450 at time. That nite my blood pressure jumped up to 160/100 and heart rate resting went up to 160 and I started having insomnia. I never had any of these symptoms in my life. Now it's been a month and still heart rate and bp is high 130 and 140/ 85 and still can't sleep. It is ruining my life can't rest causing anxiety now. I have always slept 8 hrs min usually more. Heart dr and gp drs no help. Also he gave me 100,000 mcgs isn't that a lot? Has this happened to anyone else? Does anyone have any suggestions how to lower my hr and get back to sleeping. The hospital said 3 wks to a month should be out of my system but it's little over a month. I don't know why I let him give me the shot because when I took the vitamins had similar issues on a minor scale. Can one megadose of b12 cause permanent insomnia and increased heart rate. I tried eating potassium and drinking a ton of water no help. It's like I had a shot of adrenaline that won't go away.