I would call Carnival and ask to speak with the Guests with Special Needs Dept. They are usually very helpful...
From the FAQs
Carnival Cruise Lines can provide our guests with
the following special dietary needs: Vegetarian, Low-Cholesterol,
Low-Fat, Low-Carbohydrates, Low-Sugar, Gluten Free, Indian Vegetarian
and Kosher. If you have food allergies, please advise your dining staff
Diabetes/ Medicine Storage
If you are traveling with injectable medication(s) and
need a container for disposal, please contact the Medical Center or
Housekeeping onboard. Staterooms are equipped with mini-bars which are
designed to maintain the temperature of beverages.
Please do not use them to store medications that have specific
temperature requirements. Should you need to store medicine that needs
proper refrigeration, please visit Guest Services where access to a
refrigerator is available 24 hours a day. Ships equipped with mini-bars