B12 Injections in Related Issues & Disorders Posted June 30, 2015 · Report to Admin I take B-12 shots weekly & keep my levels close to750/ 800 I retest with blood work every three months.... Wow, that surprises me, after so long. Do you have other concerns mamaw? After diagnosis, I received shots once a week for 4 weeks, then once every four weeks. I was retested and no longer need it. I do take pre-natal vitamins that are high in folic and b-12, daily. At my worst, I could not walk a strait line, nor complete a sentence.