glp 1 agonist wikipedia GLP-1 Receptor Agonists Emerging Frontiers in GLP-1 Therapeutics:

For athletes, maintaining optimal B12 levels can mean the difference between a great workout and hitting a wall

*Muscle Growth*: IGF-LR3 can stimulate muscle cell growth and differentiation, leading to increased muscle mass and strength

In other words, the preclinical signal appears against a backdrop of controlled energy intake and activity, not as a standalone effect that overrides diet

17 , e1009153 (2021)

So injecting beyond a certain point may cause your cells to fight off the excess B12 so hard that it might reduce the amount of active cellular B12 - probably not to dangerous levels, but possibly sufficient to trigger some symptoms