I can only speak for US. If I pay insurance at time of booking or before 14 days, my pre-existing conditions, if any, are covered. Trying to get whatever pre-existing conditions you have covered at a later date, is not only time consuming but more expensive. This business of pre-existing is very important for those of you with specific issues. …which is why you must read carefully or be guided by an ins rep. Ins usually pays easier when there is a fall, something broken, or medical problem while cruising.
FYI, woman I traveled with yrs ago showed symptoms of a TIA. Went to Med and they put her to bed with IV. Turns out she was dehydrated as does not drink water. Dr says common condition on a cruise. She was released 4 hrs later. $600. She did not want to take travel ins ( bridge cruise) but I told her I would not go unless she did. Dr told her if he had
Dx her with a TIA ( which I could swear she had), she would have had to be taken off ship.