Feeling worse after B12 Injection: Answering concerns. La Vie Med Spa Understanding Vitamin B12 Injections for Peripheral Neuropathy 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 When a T shot is missed, most of my Patients simply begin a new start date or wait until their usual shot day to return to schedule. The reason? Youre not going to lose the effects of T overnight