Hi Hazey,
The fact that they have insured you, and that you told them about your diabetes, does not necessarily mean that the diabetes is covered by the insurance. Unless your policy states that any condition that you have advised them of is covered, then you can assume that it's not.
Let me give you an example. For years I have been insured with Norwich Union, one of the biggest travel insurers, and the policy covered all medical conditions that I had advised them of. Then last year when we came to renew, the renewal said that we would no longer be covered for any pre-existing conditions (i.e. anything I had at the renewal date) even though they had insured them in previous years. Yet the premium still had an additional amount for my diabetes that they weren't even going to insure! I couldn't believe it so I phoned and was told this is correct. I tried several of the other big insurance companies and was told the same thing by each. Yes, they will cover me, but not for the diabetes, oh and by the way the premium is higher because you are diabetic! I ended up buying my travel insurance from this website's recommended insurers and got it cheaper and with much higher cover for medical expenses.
But the good news is that most cruise ships have a doctor, nurses, and well equipped medical suite on board (as long as your cruise isn't on the Isle of Wight ferry!!). So in the event of a diabetes related problem, it is very unlikely that you couldn't be treated on board.
