The products are not medicines or drugs and they have not been approved by the FDA to prevent, treat, diagnose, mitigate, or cure any disease, ailment or medical condition
Think of it like this, when you are starting a fire you need matches, wood, and paper
Whichever size you choose, both are drawn from the same manufacturing and testing pipeline, so purity and documentation standards do not change based on vial size
In summary, the reasons a GP surgery may refuse an early B12 injection are often rooted in a strict interpretation of established, but imperfect, guidelines, a misunderstanding of the actual science of B12 storage and metabolism, and a desire to maintain administrative consistency
That preservative is the entire reason BAC water exists it inhibits the growth of bacteria, which means a single vial can be punctured multiple times over weeks without becoming a contamination risk