For use in multi-dose applications, that is done with bacteriostatic water
For example: Proton pump inhibitors (PPIs) and H2 receptor antagonists, which are mainly used to reduce stomach acid, can affect the release of vitamin B12 from food and its absorption in the stomach
Vitamin B12 plays a vital role in supporting energy production, maintaining healthy nerve function, and forming red blood cells
Journal of Bone and Mineral Research, 2007
The short answer is simple: don't do it
For example, individuals using medications that affect Vitamin B12 absorption, vegans, pregnant or breastfeeding women, and anyone with a condition that increases the need for Vitamin B12 should speak with their doctor about getting a vitamin B12 injection