Why Injection Site Rotation Matters

Common injection sites — the abdomen, thighs, upper arms, and buttocks — each absorb insulin at slightly different speeds, but the bigger issue is repetition. Injecting the same exact spot over and over, day after day, is the main cause of a skin change called lipohypertrophy.

Lipohypertrophy is a lump or thickened area of fatty tissue under the skin. It doesn't just look or feel different — insulin injected there absorbs unpredictably, which can lead to unexplained high or low readings that seem to have no cause.

A simple habit helps: divide each site into sections (imagine a grid on your abdomen, for example) and move to a new section with each injection, working your way around before returning to the first spot. Stay at least a couple of centimeters from your last injection point and from your navel or any scars.

Check your usual injection sites every so often, by eye and by touch. Lumps, firm areas, or numbness are signs to move to a new area entirely and let the affected skin recover — this can take weeks to months.

If you switch to a site you don't normally use — say, from the abdomen to the thigh — absorption speed can shift. Check your blood sugar a bit more closely for the first few times, and mention any pattern changes to your care team.