B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics What Happens If You Inject B12 Wrong: 6 Red Flags Why Does Your Arm Hurt After Vaccine? Carreras Medical Center Lets do my first B12 injection together This is something Ive been nervous about for a long time, but today I finally did itand it honestly wasnt bad at all. I used the Union Medico needle guide