If you ever feel worse after a B12 injection, the cause is most likely not the B12 itself, but some troublesome excipient
Nonclinical studies in rodents of clinically relevant doses of GLP-1 receptor agonists showed dose-related and treatment-duration-dependent increases in the incidence of thyroid C-cell tumors (adenomas and carcinomas)
The MTHFR enzyme is responsible for converting folate into its active form, 5-methyltetrahydrofolate
This allows time for all the medication to be delivered
This can happen if you dont inject on a daily basis, but rather on a weekly, or worse monthly schedule
(PubMed) Zhang C, Luo J, Yuan C, Ding D