Three exclusions are effectively universal. Pre-existing conditions - anything that showed signs before coverage began - are excluded everywhere; it's the defining rule of the product.
Routine and preventative care - checkups, vaccines, parasite prevention, dental cleanings - sits outside accident-and-illness coverage, purchasable only via wellness add-ons that are budgeting tools rather than insurance. And waiting periods after purchase function as a short exclusion window: conditions arising before they end are typically treated as pre-existing, with orthopedic conditions often carrying the longest waits.