Japan is struggling with a growing number of foreign patients who fail to pay their medical bills, according to a recent government survey.

Nearly half the hospitals that responded said they had treated foreigners, with about one in five of these saying that had failed to collect at least part of the money owed, the Ministry of Health, Labor and Welfare said on March 27.

Japan is in the midst of a tourism boom, with record numbers of overseas visitors streaming into the country. Even more are expected for the Tokyo Olympics next year, which could leave hospitals strapped if too many bills go unpaid.

The nationwide survey covered the month of October 2018 and asked hospitals whether they had treated foreign patients and, if so, had they collected all their fees.

On average, there were 8.5 cases of unpaid bills involving foreign patients, totaling 423,000 yen ($3,820) per hospital. One reported 14.22 million yen in outstanding fees. Foreign residents accounted for 77% of these cases, while overseas tourists made up the remaining 23%.

Among foreigners visiting Japan specifically for medical treatment, 1% skipped out on their bill.

The ministry plans to use the survey findings to develop guidelines for hospitals on how to admit and bill foreigners. Measures like informing foreign patients of medical fees in advance and explaining the expenses will be included to reduce billing mishaps.

Foreign tourists are not covered by Japan's national health care system and must pay medical expenses out of pocket. About 90% of the hospitals that responded said they charged tourists roughly the same as Japanese patients.

But others billed more due to higher administrative costs -- such as interpreting services -- or because they had to deal with unfamiliar ailments. Among hospitals with large numbers of foreign patients, about 27% charged overseas tourists more than twice as much as Japanese patients.