DS2 was very ill and in an out of hospital for years as a child.
He would fight taking medication, blood tests, whatever, every single time.
I told him, that rather than the nurses holding him down to give medication, I would hold him down and do it if necessary. And I did, even though I would have to leave him with DH and have a private cry afterwards.
I always checked beforehand that he needed it, and, if he needed it I had a responsibility to make sure he had it. And I decided that it was better I forced him with love, than an apparent (lovely) strange nurse.
It's very hard, but, he remembers now that although he hated all the medical interventions, he knew that if I made him do it, it needed to be done. The reality was, he wouldn't have been alive now as a big strapping 20yo, if he had not had the medication or treatment.