Ferinject Appointment on Thursday - what was your experience?

Hi guys, I'm due to go for an iron infusion (Ferrinject) I wanted to ask what your experiences with it were? I'm a relatively healthy 28 year old female. I've never had any kind of deficiencies until recently - Vit D was non existent and of course - iron. My ferritin level is currently 16. I'm hoping to hear others' experiences so I know what to expect!