Trip cancellation insurance will protect you if you need to cancel your trip before your departure date, provided you cancel for a covered reason. Covered reasons typically include illness, injury or death of a family member or traveling companion, or your own illness, injury or death. Most policies specify that you (or the ill or injured party) must see a physician and obtain a letter from that physician stating that you are too ill or disabled to travel. You must contact your insurance provider before your scheduled departure.
Be aware that the definition of "travel companion" may include the requirement that the companion must be listed on a travel contract or other registration document. In some cases, the companion must also intend to share accommodations with you.