I recently asked a question about testing for B12 if you take a supplement. The answers seemed to suggest you should stop supplementing for between a week and 5 weeks before testing. The answers raised some questions in my mind. Is the idea to take B12 supplements until your B12 gets to a reasonable level and then stop? Or do you take it all the time to maintain B12 levels. If the latter would in not be sensible to take the test perhaps 12 hours after taking the supplement to see how much B12 was active in your body?
I have also read contradictory advice on when to take the B12 supplements - one site said it must be with food and another to take it at least an hour away from food.