How Quickly Does a B12 Shot Work? Benefits & What to Expect How Quickly Do Vitamin B12 Injections Work? Prime Aesthetics B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics Vaccine Patients Experiencing 'Vaccine Arm' Days After Injection Dermatology Times Vit B12 to resolve symptoms of burning, shooting pain, due to peripheral neuropathy, affecting the patients mobility . Typically patients have these symptoms due to diabetes, or autoimmune conditions