Medicare does not provide coverage while you are traveling outside the U.S. Certain supplemental plans may provide a limited amount of benefits, but even with this it's still a good idea to consider a travel insurance policy that will provide a greater amount of emergency medical protection.
Another important fact to keep in mind is that Medicare is considered your Primary health insurance whether they cover you or not. Therefore, when considering a travel insurance policy, you will want to pay extra attention to the type of medical benefit it will provide.
If you purchase a policy with Secondary medical coverage and need to file a claim, the travel insurance will still require you to file a claim through Medicare first. Since they will not cover, Medicare will provide a denial letter simply to show that they are not paying your medical claim. You would then be able to file through the travel insurance. With this in mind, it may be more convenient to consider a travel insurance policy with Primary medical coverage, which will save you the time and hassle of filing through Medicare first.