In recent years, consumers are becoming more health-conscious. Supplements are becoming popular as they can be purchased easily. In Japan, the “Food with Function Claims” system began in 2015; the market for supplements is expected to continue to expand. However, the use of some supplements has not been supported with sufficient scientific evidence; some products have even caused health problems. In addition, consumers may not be able to make correct decisions based on the information from the Internet. Unlike medicine, the instruction on the usage of supplements is not precise. Therefore, improving the quality of the information on the supplements will become more necessary in the future. This study aims to improve the quality of the information on supplements by surveying the disintegration and dissolution behavior of the carnitine-containing supplements and evaluated their quality. The products tested here were supplements containing commercial carnitine. Disintegration test and dissolution test were conducted according to the Japanese Pharmacopoeia. Carnitine was quantified by high-performance liquid chromatography. The disintegration tests revealed that the products had different disintegration times, varying from 35 to 100 minutes; some products took more than 5 hours to disintegrate. Thus, some products had a slow rise in their dissolution rate. These results suggest that the carnitine-containing supplements used in this study may affect the absorption process. Therefore, in the case of oral administration, the expected effect might not be achieved depending on the product.