La L-cystine est l'acide amin lui-mme
If youre looking at preventative and maintenance measures, Performance Lab NutriGenesis Multi contains a precisely dosed optimal form of B12 along with 23 other high quality bioidentical nutrients

Major Ingredients Water, Glycerin, Dipropylene Glycol, Propanediol, Hippophae Rhamnoides Water, Caprylic/Capric Triglyceride, PPG-13-Decyltetradeceth-24, Hydroxyacetophenone, Caprylyl Glycol, Carbomer, Tromethamine, Hydrogenated Lecithin, Glutathione(600 ppm), Cetearyl Alcohol, 1,2-Hexanediol, Disodium EDTA, Stearic Acid, Dipotassium Glycyrrhizate, Terminalia Ferdinandiana Fruit Extract, Butylene Glycol, Lecithin, Pentylene Glycol, Acetyl Glutamine, Sodium Hyaluronate, Polyglyceryl-10 Stearate, Panthenol, Folic Acid, Bacillus/Soybean Ferment Extract, Oligopeptide-1, Hexapeptide-11, Oligopeptide-2, Oligopeptide-3, Sodium Ascorbyl Phosphate, Hydrolyzed Pea Protein, Madecassoside, Phytosterols, Squalane, Olea Europaea (Olive) Fruit Oil, Tocopherol, Niacinamide, Hyaluronic Acid, Hydrolyzed Hyaluronic Acid, Hydroxypropyltrimonium Hyaluronate, Hydrolyzed Sodium Hyaluronate, Potassium Hyaluronate, Ceramide NP, Butyrospermum Parkii (Shea) Butter, Ethylhexylglycerin, Biotin, Sodium Hyaluronate Crosspolymer, Pyridoxine, Cyanocobalamin, Riboflavin, Thiamine HCl, Retinol, Bioflavonoids, Sodium Acetylated Hyaluronate, Menadione, Acetyl Hexapeptide-8, Copper Tripeptide-1, Palmitoyl Pentapeptide-4, Linoleic Acid, Beta-Carotene, Fragrance Ingredients subject to change at manufacturer's discretion

As with any supplement or research compound, documentation transparency and regulatory compliance should be considered before use