NHS B12 therapy is evidence-based for documented deficiency, using hydroxocobalamin 1mg intramuscularly with standardised protocols
Vitamin B12 is vital for energy, nerve function, and red blood cell production
For example, while the injection covers B, B, B, B, B, you still need other vitamins (like vitamin C, B folate, B if not supplemented separately, etc.) and minerals (iron, zinc, etc.) from food
This is likely due to a reduction of peptide interactions (mainly A5 Cagri ) with ECL3 that is a consequence of the engagement of the lipidated N-terminus with the top segment of TM5/ECL2, facilitating flexibility of ECL3
A day or two during shipping is fine