We've had a couple health snafus in our years of cruising. The medical center has been quite thorough and helpful to keeping our vacation on track. Also, we carry a few things that are specific to our health issues. If needed, we have advance plans which our providers approved. We don't bother contacting the MC unless those fail.
Just a suggestion: People with a chronic condition should talk to their provider about an action plan for flares and other common issues that may arise while away from home. Also, be sure to bring an extra supply of medication. A supply of blood glucose monitor supplies and glucose wafers, a supply of prednisone, a urinary catheter and/or other supplies or equipment may make a big difference in avoiding an urgent / emergent situation.