While on a rainforest hike in Costa Rica, you catch your foot on a liana vine and crash to the ground. As your ankle swells to alarming proportions, you manage to hobble back to the jeep and reach a nearby private hospital. But when you pull out your U.S. health insurance card, the hospital staff shakes their heads. It's cash up front or nothing.

This happens more often than you think. Travelers assume their health insurance works overseas — but not every insurance plan will cover you for every destination and situation. If you're planning a trip abroad and wondering, "Do I need travel insurance if I have health insurance?” here's how to find out.

Do I need travel insurance if my insurer offers overseas health insurance?

When you're planning an overseas trip, you should call your insurance company beforehand to ask if your plan includes overseas health insurance. Some do, some don't, and some will cover you only in certain situations. The U.S. Department of State suggests some questions to ask your insurer, including:

• Does my plan cover emergency expenses abroad such as returning me to the United States for treatment if I become seriously ill?
• Do you require pre-authorizations or second opinions before emergency treatment can begin?
• Do you guarantee medical payments abroad?

While we can't speak to what your specific insurance policy will cover overseas, here are the general policies of a few major insurers.

Anthem Blue Cross and Blue Shield does offer travel coverage, but draws a line between "urgent care" and "emergency care." Emergency care, Anthem says, is requires by an injury or condition severe enough to result in "placing the Member's physical and or mental health in serious jeopardy; serious impairment to bodily functions; or serious dysfunction of any bodily organ or part."

"Urgent care," on the other hand, "may not be covered to the same extent as emergency care." For example, Anthem says, a fever not higher than 104° is considered urgent, not emergency care.

Aetna states that "emergency care is covered 24 hours a day, seven days a week – anywhere in the world." An emergency, Aetna says, "is a situation in which you could reasonably expect that the absence of immediate medical attention could result in serious jeopardy to your health, or if you are a pregnant woman, to the health of your unborn child." Cigna advises members to check their policies: "Outside of the U.S., coverage is limited to emergency services as defined in the policy."

In short, your definition of "emergency" may differ from your insurer's definition, and you may find yourself on the hook for medical expenses you thought were covered. That's why buying travel insurance is so important, U.S. News reports, because it "can help fill any gaps in domestic health insurance coverage."

Do I need travel insurance if I have Medicare?

The short answer: Yes. According to Medicare.gov, health care you get while traveling outside the U.S. isn't covered. There are a few rare exceptions. If, for instance, you're traveling through Canada to get to Alaska when a medical emergency occurs, and a Canadian hospital is the nearest facility, Medicare may cover your treatment.

You can purchase a Medigap policy to cover emergency care received outside the United States. This policy pays 80 percent of the billed charges for certain medically necessary emergency care outside the U.S. after you meet a $250 yearly deductible. Medigap coverage has a lifetime limit of $50,000.

The OneTrip Prime Plan from Allianz Global Assistance, on the other hand, has no deductible and offers benefits for 100 percent of losses due to covered medical emergencies, up to $50,000 per trip.

Three things to know about travel insurance vs. overseas health insurance

1. Travel insurance isn't the same thing as health insurance.
   Travel insurance with emergency medical benefits offers just that — benefits for losses due to covered medical and dental emergencies. It doesn't cover preventive, routine or elective medical care. Appendicitis in Amsterdam? Probably covered. Rhinoplasty in Rio? Not covered.
2. Travel insurance includes some major benefits that health insurance plans don't offer.
   When you buy international travel insurance from Allianz Global Assistance, you're not just getting benefits to cover emergency medical expenses. You also get emergency medical transportation benefits, up to $1 million (depending on the plan you choose) to travel to the nearest appropriate medical facility or to return home. This is huge. If you need to be airlifted to a hospital, or you need a nurse to escort you home, the costs will be exorbitant without travel insurance.
   
   Travel insurance also includes trip cancellation and interruption protection to reimburse you for non-refundable trip payments, in case you have to cancel your travel because of covered illness, injury or another covered reason.
3. Travel insurance includes personal, one-on-one help in emergencies.
   Call the 24-hour assistance hotline from anywhere in the world, and our call center experts will help you, including serving as interpreters and even arranging to fly a family member to your bedside, if necessary.

We know this gets confusing, and we're here to help. Call our travel insurance advisers anytime at 1-866-884-3556, and they can talk you through your travel insurance options and coverage needs. Travel happy!

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