This study was conducted clarify the usage of health foods, supplements, and functional health foods in conjunction with the level of awareness of their interaction with pharmaceuticals. The data consisted of responses from a questionnaire survey of people who visited an insurance pharmacy and of measurements of the calcium content of health foods commonly available via online sales that are likely to be used in combination with pharmaceuticals. Based on this information, we considered the issues involved. The survey was completed by 189 respondents, 58 (30.7%) of whom used health food products. Although more than half (52.9%) of the respondents (100 people) were aware of health food-drug interactions, none of them understood the specific details. About half of the respondents obtained information on health food-drug interactions from the Internet, magazines, newspapers, and other media, while only a small number of respondents obtained information from physicians, pharmacists, and other health-care specialists. Among the survey respondents, 10 (5.3%) were osteoporosis patients, 7 of whom were taking vitamin D₃ preparations as medicines, with 3 of the 7 using health foods. The calcium content in health foods sold on the market differs depending on the manufacturer in terms of purity and composition of the raw materials used, even if the products may have similar name. Some products contained calcium even though the product name did not indicate calcium or minerals. The use of multiple types of health food products could unintentionally cause hypercalcemia due to interactions with pharmaceuticals. We concluded that sufficient awareness of health food-drug interactions is lacking and should be addressed as a health-care issue.