A medical bill arriving in an envelop.

It's awful to become ill or get injured on vacation. It's even worse if you get hit with a big medical bill when you get home.

If you have a medical crisis that requires a trip to the emergency room while traveling in the U.S., “your plan should cover you regardless of location,” says Sean Malia, a senior director at eHealth, an online site for buying health insurance.

But if you have a more minor problem—say, you sprained your ankle or suspect your child has strep throat—how the bill is covered can depend on where you seek care and the type of insurance you have, says Cathryn Donaldson, director of communications at America’s Health Insurance Plans, a trade association for insurance companies.

Your insurer may treat it as an out-of-network claim, and you could be on the hook for a larger portion of the cost or the whole bill.

To protect yourself from a surprise medical bill, put these tasks on your pre-trip to-do list.

1. Pack your medical information. Make sure you have an up-to-date insurance card in your wallet. Put your healthcare providers’ contact info in your phone in case you need a referral. Also, take a list of your medications and dosages.

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2. Don't forget your meds. If your current stock of Rx drugs won’t last your trip, ask your insurer for a “vacation override” so that you can get an early refill. If you run out while you’re away, call your doctor. Most insurers contract with national retail drugstore chains.

3. Check what your insurer covers. Ask your insurer ahead of time how it defines an emergency and what will be covered if you need treatment away from home. Request a list or see whether your insurer has a mobile app so that you can find ERs, urgent care centers, pharmacies, and doctors covered along the way.

4. Give your doctor a heads-up. If you have a chronic condition, contact your physician before you travel and ask for a referral to doctors who could treat you at your destination.

5. Take advantage of telemedicine. Most insurers offer telehealth services, which allow you to do a video consultation with a doctor via your smartphone, computer, or tablet. Telemedicine usually costs less than seeing a doctor in person, and some teledocs can prescribe short-term medication.

Editor's Note: This article also appeared in the July 2018 issue of Consumer Reports magazine.