b12 self injection kit Shots at Home: How, Where & How Often to Inject Yourself tells the Mayo Clinic b12 self injection pen China

This is also where the supply-versus-stability point from the reconstitution section bites: if a reconstituted 10 mg vial holds ~66 doses but the solution is only reliably stable for a few weeks, plan the reconstitution volume so you are not left discarding drug you paid for

Vitamin B12 is not considered dangerous for most men, but excessive supplementation may mask underlying health issues, such as folate deficiency, if not managed with proper medical supervision

The preventive efficacy of methylcobalamin on rat peripheral neuropathy influenced by diabetes via neural IGF-1 levels

Preparing the Injection: Vials are multi-use