How Quickly Do Vitamin B12 Injections Work? Prime Aesthetics Vitamin B12 Booster Shot B12 Injections McCartan's Boost Your Energy with ! Symptoms of low B12 includes: Constant fatigue Lack of energy Memory problems Pins and needles sensations Depression or mood B12 Shots for Energy: Do They Work, Who Needs Them & What to Expect Greenwich Medical Spa B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics