Hi, just looking for some advice on b12. I was told by blue horizon my levels of b12 were low at 270, so I saw my GP who didnt seem to concerned, but said I could buy some over t he counter supplements if I wished. I bought Jarrow 1000 b12 off amazon. When I next saw my GP three months later after a blood test it had gone up to 750. Trouble is the new GP said they couldnt test for P.A now as the results would be scewed. Surely they should have done the tests before they told me to take the supplements. So now I am wondering how long I need to be off the supplements before they can do the test and if coming off will do any damage. Any help appreciated.