b12 injection cause diarrhea Vitamin Side Effects: Risks of Excess Intake Vitamin B12 Injections (Cyanocobalamin Injections)
Description
B12 is contraindicated in Lebers Disease (a hereditary optic nerve atrophic condition), clients with chronic liver and/or kidney dysfunction, or abnormal red blood cells (megaloblastic anemia)

Vitamin B12 is also known for boosting metabolism, which can aid in weight loss

Evaluation of safety and effectiveness of NAD in different clinical conditions
How Does B12 Affect Metabolism