Most existing tools for measuring health literacy (HL) focus on reading comprehension and numeracy in English speakers. The aim of this study was to develop a generic HL measure for Japanese adults.

A questionnaire survey was conducted among participants in multiphasic health examinations at a Japanese healthcare facility. HL was measured using the 14-item health literacy scale (HLS-14) that was adapted from the HL scale specific to diabetic patients developed by Ishikawa and colleagues. The 14 items consist of five items for functional HL, five items for communicative HL, and four items for critical HL. The reliability and validity of the HLS-14 were assessed among 1,507 eligible respondents aged 30–69 years.

Explanatory factor analysis produced a three-factor solution that was very similar to the original HL scale. Cronbach’s alpha indicated satisfactory internal consistency of the functional, communicative, and critical HL scores (0.83, 0.85, and 0.76, respectively). There were no floor or ceiling effects in each HL score. Confirmatory factor analysis revealed an acceptable fit of the three-factor model (comparative fit index = 0.912, normed fit index = 0.905, root mean square error of approximation = 0.082). When the two groups with a total HL score above and below the median (50), respectively, were compared, those who could obtain medication information satisfactorily and those who wanted to participate in making medication decisions were more frequently observed in the group with the higher score.

The HLS-14 demonstrated adequate reliability and validity as a generic HL measure for Japanese adults. This scale can be utilized for measuring functional, communicative, and critical HL in the clinical and public health contexts.