alt Hacker NewsInjection drug user here. We're advised to rotate injection sites but the largest issue is actually the insulin (most of it diffuses into the bloodstream but there is a local effect, usually taking the form of increased fat accumulation at sites of repeated injection), not the "making holes in the skin" part.
I don't know the pharmacokinetics of GLP-1 drugs but my guess is that they don't have the same sort of effects on SC tissue?
Before I had a CGM I did somewhere around 20,000 blood glucose tests over the course of a decade using about 1 cm^2 of forearm and the skin there is clearly not in great shape -- but it's worsened on the level of "looks like the skin of someone who is a decade older or spent too long in the sun" rather than anything medically problematic.
> I don't know the pharmacokinetics of GLP-1 drugs but my guess is that they don't have the same sort of effects on SC tissue?
They do, but nothing like insulin does. GLP-1 drugs are more centrally and viscerally active than subcutaneously active, so the effects locally are more related to the physics of injecting solutions subcutaneously than the drugs themselves. They're also much smaller doses than are needed for insulin in general, so the volume averaged over a week is pretty tiny.
Also, as a result of the relative lack of local activity, injection sites are basically unlimited (anywhere from above the knee to above the elbow, except the neck) without fear of lipohypertrophy in the local area.