--to your nerve pain, why not try taking a B12 supplement, such as 1000-5000mcg (1-5mg) of methylcobalamin, several times a week or even every day?

Much more convenient, and likely much less expensive, than injections--and the dosing should provide, though 1-2% passive absorption, enough B12 to maintain stores, even if you have pernicious anemia or some other absorprtion issue.