I had a detailed chat with the practice nurse who gives me the injection, due to different symptoms. I was ok for a couple of weeks after having my b12, but from then I would start getting a blood blister in my mouth every couple of days and by the time my next jab was due, I would be getting two or three of them everyday, as well as at least one ulcer a week, blurred vision and pins and needles in my hands and feet. She suggested having it every four weeks but to check what my team said first. They insisted to try it every eight weeks until my next appt, then they would review. The nurse wasn't happy, so suggested sticking to the eight weeks as my team said, plus buy a decent b12 slow release to try and back it up until my next appt.