I would not buy it already reconstituted. Is it methyl or hydroxy? If Methylcobalamin: it is less stable, particularly when exposed to Light and Heat. Over time, degradation products can include hydroxocobalamin and other forms. keep it wrapped in foil and in a dark place. 0.3 ml per day, or 1ml 2x /week.

@Natasha Decker if it is Methylcobalamin and it stings when you inject it, then it has already started degrading or fully degraded to Hydroxy and other cobalamins. Methylcobalamin doesn't sting upon injecting. Hydroxy does. They both work on supporting the liver but in different ways. If your goal is methylation, then you would want it to stay in its methyl form and stay as stable as possible.

my doctor prescribed it as a bioregulator