Hi Tiffany I also have PA, you cannot overdose on B12, too much does no harm , look at the PA society website, some European countries give it every month, and you can buy it over the counter. It seems only to be the UK that Gps restrict B12, everyone is different and the B12 use by the body is different from day to day and person to person, you should be able to have a dose of it when you feel the need, preferably before the symptoms return. Also you don't need to have your levels checked. Your GP should be treating your symptoms, I have mine every 8 weeks, sometimes after 6 weeks. The NICE guidelines advise every 8 weeks if you have neurological symptoms , soda you ever get pins and needles in your hands or feet or jumpy legs or any numbness in fingers and toes especially 8-10 weeks after your last injection? If so you need it 8 weekly, good luck