In contrast, cyanocobalamin, a synthetic form of B12, must be converted into Methylcobalamin or adenosylcobalamin in the body before it can be used
Most supplement companies use the racemic R/S mix because it is cheaper to manufacture

Key sources included the US Food & Drug Administration (FDA), European Food Safety Authority (EFSA), National Institutes of Health (NIH) Office of Dietary Supplements, National Center for Biotechnology Information (NCBI/PubMed), US Department of Agriculture (USDA) Agricultural Research Service, World Health Organization (WHO) Global Health Observatory, Organisation for Economic Co-operation and Development (OECD) Health Statistics, EU Eurostat Health Database, National Center for Health Statistics (NCHS/CDC), International Food Information Council (IFIC), Council for Responsible Nutrition (CRN), Natural Products Association (NPA), United States Pharmacopeia (USP), International Nomenclature of Cosmetic Ingredients (INCI), Personal Care Products Council (PCPC), Codex Alimentarius Commission, European Medicines Agency (EMA), Japan Ministry of Health, Labour and Welfare (MHLW), China National Health Commission (NHC), Health Canada, Therapeutic Goods Administration (TGA) Australia, and national health ministry reports from key markets

Many clients report a noticeable energy lift within 2448 hours of a B12 shot
Handog EB, Datuin MS, Singzon IA