Vegans, people with various genetic issues, athletes, and people who want to achieve their ideal body weight and have L Carnitine deficiency often choose to supplement their diet with oral L-Carnitine or L-Carnitine injections designed to provide an extra boost of energy and encourage fat burning
This sounds obvious

Cyanocobalamin is a manufactured form of vitamin B 12 used to treat vitamin B 12 deficiency.[2] The deficiency may occur in pernicious anemia, following surgical removal of the stomach, with fish tapeworm, or due to bowel cancer.[6] It is less preferred than hydroxocobalamin for treating vitamin B 12 deficiency.[4] It is used by mouth, by injection into a muscle, or as a nasal spray.[4][5] Cyanocobalamin is generally well tolerated.[7] Minor side effects may include diarrhea and itchiness.[8] Serious side effects may include anaphylaxis, low blood potassium, and heart failure.[8] Use is not recommended in those who are allergic to cobalt or have Leber's disease.[6] Vitamin B 12 is an essential nutrient meaning that it cannot be made by the body but is required for life.[9][7] Cyanocobalamin was first manufactured in the 1940s.[10] It is available as a generic medication and over the counter.[4][7] In 2019, it was the 155th most commonly prescribed medication in the United States, with more than 4 million prescriptions

The experiments were performed according to the criteria of the new investigational drug application
doi: 10.1016/j.regpep.2013.03.026
MIC B12 injections are generally considered safe for most patients when administered under the supervision of a trained medical weight loss provider