I can't think of any way in which this would happen
You dont need a GP referral, which is why its popular for people looking to address symptoms quickly
If improved health and vitality is what you're after, you should also aim to get plenty of B12 through your food, incorporating health-promoting fortified foods like nutritional yeast, natural fortified cereal, and fortified plant milks into your diet (and maybe a few vegan gummy vitamins on top to help with specific issues)
The Vitamin B12 injection is an effective way to treat a deficiency
Warning Signs of Improper Dosing TTaking too little B12 may leave deficiency-related nerve symptoms untreated, while improper use can also lead to unwanted effects or missed diagnoses
AdvaCare Pharma produces a wide range of vitamin B injections, including Vitamin B1 Injection (Thiamine HCl), Vitamin B6 Injection (Pyridoxine HCl), and Vitamin B Complex Injection