Many policies now require you to get prior approval for a planned hospitalization, with a penalty of reduced benefits if you don't. They may be more lenient with emergencies but still require notification as soon as possible after the emergency. Some may also limit the choice of hospitals or doctors you can use. Even if you don't need pre-approval, informing an insurer before a hospitalization is a good idea since they can usually pay the hospital directly for your stay. In most cases, you must pay physicians, labs, etc.
Some policies require a completed claim form - others, just the original bill.
In almost all cases, you should get the bill in English or supply an English translation - it tends to smooth the path to reimbursement. This is obviously more useful when you're in a non English-speaking area, but you can use it wherever you are in the world. But, be aware that no policy offers evacuation just because you would prefer it. If the emergency can't be treated locally, you will be evacuated to the nearest major facility capable of providing a decent standard of care. The definition of ' nearest ' and ' decent ' are decided jointly by the Emergency Help Center and the insurance company.