I’ve just read and compared the manufacturer instructions for Hevert and Pascoe.
Hevert - first few weeks 1ml (500mcg) twice weekly followed by 100mcg per month. Discard remaining b12 in ampoule.
Pascoe initially 1500mcg twice weekly, also followed by monthly dose of 100mcg. So 1/15th of an ampoule!
It seems odd that nowhere does Hevert advise to inject a full ampoule and the small monthly maintenance dose for both brands is just a fraction of the amount supplied.
Both do say unless otherwise specified by a doctor, but it’s surprising all the same.