 [ Symptoms ] what size needle is used for b 12 injections i am terrified of needles and dr wants to give me b 12 injections [ Disease ] b 12 comes in different forms and different viscosities but the thinner aqueous form can be injected with a tiny needle that is near painless the thicker longer lasting solutions may require a slightly bigger needle but they are not that bad do not worry why is your doctor suggesting b 12 there needs to be a real medical reason