Does it matter which day I inject on?

Answer

For the weekly products, consistency matters more than the specific day, and the labels describe how to change days.

In more detail

A weekly injection with a half-life of roughly five to seven days is designed to hold a fairly level concentration between doses, which only works if the gap is roughly constant. Labels for the weekly products describe changing the day of the week as long as the interval rules are respected — tirzepatide's label requires at least 72 hours between two injections, which is what makes shuffling a day forward a labeling question rather than a preference.

Source

Approved labeling for the weekly incretin products.

Educational use only, never medical advice. No doses.