The recent kidnapping of four Americans in Mexico highlights a common practice for many people in the U.S.: traveling to other countries for medical care that either is not available at home or costs a lot less.

The four were abducted — leading to the deaths of two — during a trip to Mexico that one relative said was for cosmetic surgery.

People leave the U.S. for dental procedures, plastic surgery, cancer treatments, fertility treatments, organ and tissue transplantation and prescription drugs, experts say. Besides Mexico, other common destinations include Canada, India and Thailand.

Josef Woodman, the chief executive of Patients Beyond Borders, which serves as an international healthcare travel consulting agency and patient guide for people seeking care abroad, estimates that about 1.2 million Americans per year travel to Mexico for medical procedures.

Here’s a closer look at the practice.

Medical Tourism Growing 

Medical tourism has been growing in popularity for years, according to Lydia Gan, an economist at the University of North Carolina at Pembroke who studies the practice.

This travel is popular with people who have no health insurance or plans that make them pay thousands of dollars before coverage begins.

Complex dental treatments like root canals, veneers and full mouth reconstructions are among the most popular procedures, Mr. Woodman said. Los Algodones, near the California-Arizona border, is known as “Molar City” because it caters to this market.

Big employers also sometimes send people covered by their insurance to other countries for hip or knee replacements or bariatric surgery. Some also send people to Mexico for expensive prescription drugs.

Cost is a huge factor. Care in countries like Mexico can be more than 50% cheaper than it is in the United States, according to Jonathan Edelheit, CEO of the non-profit Medical Tourism Association, an industry trade group.

And cosmetic surgeries, like tummy tucks that cost thousands of dollars, are largely uncovered by U.S. health insurers.

Weighing & Reducing Risks

While traveling for health care to certain areas of the world can be dangerous, experts said that for most patients, the risks have more to do with the medical procedure than the journey to obtain it.

Patients can take steps to lessen risks of receiving care in another country.

They should heed U.S. government travel alerts about their intended destinations, Edelheit said.

Trip safety also can be enhanced if a medical tourism agent works with the patient, Gan noted. Hospitals or care providers often will have someone pick patients up at the airport and take them to their doctor appointment or hotel.

Patients also should do research on care quality before looking at prices, Edelheit said. They should learn where their potential doctor received training and look for any accreditations or certifications.

Mr. Woodman recommended seeking out hospitals accredited by Joint Commission International. It’s important for patients to ensure that anyone giving them medical care has received proper training, said Dr. Patricia Turner, executive director of the American College of Surgeons. That includes not just the doctor performing surgery, for example, but also the person administering anesthesia or interpreting X-rays.

“They really need to make sure they are going with the best of the best,” he said.

The C.D.C. recommends that patients schedule a consultation with their U.S. health care provider before leaving the country for medical care, said Allison Tayler Walker, lead of the epidemiology and surveillance team in the Travelers’ Health Branch at the agency. The C.D.C. also advises patients to arrange follow-up care ahead of time with the professional who conducts the procedure abroad, as well as with a primary physician in the United States.

The risk for patients may not end after the procedure. If someone has complications after returning home, it may be hard for their U.S. doctor to learn the details about the care received during a trip.

There are also specific risks that come with certain interventions — for example, doctors caution against flying too soon after some surgeries, Dr. Béland said, because the procedures can make a person more susceptible to blood clots.

Patients also may find it difficult to sue their doctor or hospital in Mexico.