In short, its because of convenience
Potential Benefits: The combination is suggested to potentially enhance fat reduction (especially abdominal fat), improve muscle mass and recovery, and potentially minimize the side effects associated with conventional GH therapy
B12 also promotes healthy brain and nerve function, aids in fat metabolism, and helps prevent anemia-related exhaustion
(PubMed) Tangney CC, Tang Y, Evans DA, Morris MC
Methylcobalamin is especially effective in maintaining nerve health because it is the active form that directly participates in nerve regeneration and repair
Nausea Diarrhoea: You could experience loose, watery stools more frequently than normal