side effects b12 injections How Long Does a Shot Last? Cyanocobalamin - Wikipedia

Vitamin B12 deficiency is associated with cognitive problems (problems with thinking, judgment, and learning) and memory issues

The timeline is too short

Short-Term Observations in Study Protocols Within the first one to two weeks of a research protocol, study data begin to show early physiological markers, including changes in cellular hydration and glycogen retention, along with indicators consistent with reduced markers of muscular stress in trained tissue models

So my best friend in the whole world, I can name his name and Jim Brown, who I was friends with for 28 years, like he was even a mentor to me, and a lot of the things that I learned, he was actually at one time a professional bodybuilder