How Quickly Do Vitamin B12 Injections Work? Prime Aesthetics Vitamin B12 Injection Dosage for Adults: 7 Key Medical Guidelines Liv Hospital How Long Does a B12 Shot Last? LiveVibrant Wellness Guide B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics Hi I bought the B12 injectable liquid but there's no use by date on it or how long you have to use it once it's opened. Anyone know the answer? TIA x