Deltoid arm triangle area can be used for both IM and SQ injections.
What makes difference between types of injection is depth of needle and angle of needle. Other factors to consider are viscosity of medication which would affect absorption rate of med through the tissues in whether I would use same area for multiple injections.
Insulin is absorbed fairly quickly though skin tissuse so perfectly safe to give other medication/immunizations in same area at later time during shift.
It's pretty rare that you actually inject exactly same area of skin using same trajectory for injections...most are off by few millimeters/cm.
a. Give each immunization in seperate arm so can tell if reaction occurs.
This can cause patient to have TWO sore arms.
b. Give each immunization in same area, 1" apart so only one arm sore.
If I was planning to give all three at same time, would use abd for SQ insulin, deltoids for injection.
My preference while working in hospitals was to always rotate sites to avoid long term problems, especially when pt had long term hospitalization. Short term stay, didn't worry about need to rotate so much.