How Long Do the Benefits of a Vitamin b12 Injection Last? Feeling tired, foggy, or run down? It could be a B12 deficiency Weekly B12 injections help support: Increased energy + reduced fatigue Sharper focus + better mood Boosted How Long Do The Benefits of a Vitamin B12 Injection Last? How Long Does Vitamin B12 Take to Work? Timeline & Signs Performance Lab Wow guys, you've been gate keeping!! Got my first B12 injection last week and it's like I am awake for the first time since having kids 20 years ago It's