vitamin b12 injections other names Forms Vitamin B12 - Wikipedia

They might need special dosing because of aluminum toxicity and clearance issues

Commonly reported mild effects in anecdotal community reports include nausea, fatigue, and injection site irritation

doi: 10.1016/j.freeradbiomed.2008.03.002

Even if the product could be reclassified to make it available for sale in pharmacies, it could not be used more frequently than every 2 3 months, so reclassification to a Pharmacy medicine would not help those who require more frequent injections. and then they also state: Our current advice to private clinics administering vitamin B12 injections which are not licensed medicinal products intravenously for non-medicinal purposes is that we do not regard these to be medicines and that they fall outside of the remit of the MHRA

Protein Kinase A (PKA) Activation: Elevated cAMP levels activate PKA