do b12 injections cause constipation Vitamin | Energy Boost Vitamin B12 Shots: Uses, Intake
Description
The competition between NAD + salvage and the methylation of NAM suggests that NNMT may reduce the oxidation of fuel and increase the storage of fat by regulating the formation of NAD + (Trammell and Brenner, 2015)

Enhanced Cognitive Function: Support for memory and concentration
PMID 18042717

Therefore, most Americans have more than enough vitamin B12 in their systems and do not need to worry about increasing their B12 levels