I agree with Sonny. I am a RN, I work in Medical ICU, in a Level 1 trauma center. Anyways, I asked for a tour of the medical facility on a RCCL ship. I don't remember which ship it was.
They had 2 or 3 rooms, one of them was there ICU room. They had a ventilator, (breathing machine), they are able to do basic blood work, xrays. What really impressed me, is they can also do blood transfusions. They said they keep a few units for a real emergency. They said most of there "emergencies" where diabetic, GI and cardiac in nature. The RNs on this ship were from England. Britain has VERY competent RNs. They are HIGHLY skilled. You are in good hands with them. I am sure the MDs would be just as competent, I did not meet the Dr on the ship, just the RNs. My mom was seen in a ship doctors office on Princess, to rule out a heartattack. They did rule it out. She told me what they did, I don't remember now, but I do remember I thought it was appropriate. I would feel very safe, taking a diabetic family member on a cruise. If she is very brittle, maybe consider taking out trip insurance. Hope this helps. Enjoy your first cruise.