SUNDAY, Oct. 29 (HealthDay News) -- Whether you're jetting to New Delhi on business, setting sail on the Mediterranean, or roughing it as a volunteer in Guatemala, you've got to be prepared for your medical needs.

Even a weekend in Paris requires some advance planning, travel health experts advise.

"I think maybe a lot of people don't do much of the thinking, they just do the packing," said Dr. Mark Wise, a family physician in North York, Ontario, Canada, and author of The Travel Doctor: Your Guide to Staying Healthy While You Travel.

The amount of preparation required for a trip abroad, of course, depends on many variables. You'll need to consider your destination, the length of your trip, the time of year you're traveling, and your current health condition, among other factors. Failing to do your homework, experts warn, could spoil the whole excursion.

For instance, "There's the one-week, let's-go-to-Mexico traveler who thinks they're going to an all-inclusive resort with eight stars and don't think they need anything," said Wise, who serves as medical advisor to several organizations. The truth is that traveler is at risk for diarrhea, hepatitis and the kind of accidents that occur when people drink too much or engage in activities they might not normally do, like parasailing, he explained.

Also vulnerable are the millions of immigrants who regularly travel back to their homelands. Sometimes, they think they're immune to indigenous health conditions and don't take proper precautions for themselves or their children, Wise said.

Long-term travelers who venture to poor and rural nations with volunteer organizations also need to plan ahead, he cautioned, because, while some organizations are really well-prepared, others aren't.

Also, where you're headed often will determine what you pack and whether you require certain vaccines to enter a country.

"You really need a little bit of in-depth knowledge of exactly where you're going," Wise advised, "and hopefully a travel doctor of your own research can help you with that."

You also need to contact your health insurer to find out what medical services, if any, your policy will cover abroad. Neither Medicare nor Medicaid provides coverage outside the United States, said Brendan Sharkey, vice president of individual programs at HTH Worldwide, a Radnor, Pa.-based company that sells travel health insurance. Generally, health insurance offered through an employer or purchased individually provides only limited coverage of services abroad, he said.

"Typically, they're only going to cover you for emergency services, and that's going to be incumbent upon you to prove that it's an emergency," he said. But people often require care for more routine ills, he added. "So if I have stomach pains and I go to an internist in Paris, that's not going to be covered."

What's more, very few insurers will pay for medical evacuation back to the United States. An evacuation can easily cost $10,000 and up, according to the U.S. State Department.

But you can fill those gaps in coverage by purchasing travel health insurance. Depending on your age, it will cost you from $1.50 to $3 per day, on average, for about $1 million of medical insurance coverage plus an additional $500,000 of medical evacuation insurance, Sharkey said.

The U.S. Centers for Disease Control and Prevention says people who are traveling abroad for an extended period, who have underlying illnesses, or who are participating in activities that put them at risk for injury are encouraged to consider a travel insurance policy that includes emergency transport.

"No matter where you go," Wise cautioned, "you've got to be insured because anything can go wrong wherever you go."

You should also find out where you'll get your medical care before you need it, he urged, especially if you're a long-term traveler.

"I joke about the first thing they look for is the Internet cafe. That's OK," Wise said. "Then they should look for where they're going to get a clean needle and where they're going to see the doctor and where they can get their malaria tests."