Tony doesn't skip a beat to take the syringe. He gets her hesitation the moment he sees it. Obviously, she wouldn't know enough about a human body.

He steps in and straightens out Peter's arm. The screen from his suit helmet zoomed in and highlighted just where he needed to put the needle. As he sticks it into Peter's skin, he remembers how much the boy hates shots. Well, this one just might be his favorite now as it was saving his life.