Never combine Retatrutide with other GLP-1 or GIP agonists like semaglutide, tirzepatide, liraglutide, or dulaglutide due to overlapping mechanisms and severe side effect risk
Nothing detectable happens on day 29, which is exactly why the question keeps getting asked
These are more considerations of medications affecting vitamin status (rather than the vitamin affecting the medication), but they illustrate the clinical judgment required when co-administering this injection with certain treatments
Along those lines, many assume that B12 improves brain and cognitive function due to its ability to reduce homocysteine levels
Vitamin B Complex, Menorrhagia, and Cancer: A Critical Review. American Journal of Obstetrics and Gynecology 54.4 (1947): 611-617
For weight-loss evidence context, review Mayo Clinic information on B12 injections and weight loss