The dysphagia diet for hospitalized patients is necessary to ensure their physical stability, and various viscous materials are used for liquid balance. The aim of this study was to evaluate time-dependent modulation of viscous material solutions, measured using the Sine Wave Vibro Viscometer. We also developed an original viscosity index based on the relationship between material concentration and stable viscosity at 5 min after mixing, as stated in the Japanese Dysphagia Diet 2013 recommended by the Japanese Society of Dysphagia Rehabilitation Dysphagia Diet Committee. Comparison of the concentration of viscous materials in the viscosity range 50-150 mPas showed that minimum and maximum concentration was 0.43% and 1.06%, respectively, and these estranged approximate twice. These results suggest that it is difficult to prepare solutions with equal viscosity using different materials, because the materials or diluent for therapeutic diets are different in each hospital. It is expected that the viscosity index will help to raise healthcare professionals’ awareness about the importance of material quantitation and that it will become one of the tools used in nutrition education, dietary intervention, and interprofessional collaboration in healthcare.