This article reports a study about a design process and empirical testing of a practical screening tool aiming at identifying individuals with limited everyday health information literacy (EHIL). First, the relevance of the two related concepts "health literacy" and "health information literacy" are discussed. Secondly, a 10-item tool based on the operationalization of the Medical Library Association's definition of health information literacy is presented. To pilot the tool, a survey (N=217) was conducted in an Upper Secondary School in Finland in April 2011. The statistical analysis consists of frequency analyses, f-tests for means (ANOVA), correlation analyses (Pearson's r, two-tailed), cross tab-analyses (chi-square) and a factor analysis (extracted and rotated via unweighted least squares and varimax respectively). The results prove that the EHIL screening tool can be used for dividing people into groups according to their level of health information literacy. Results also indicate gender differences: the female students were more motivated to obtain health information than the male students and they to a greater extent preferred to obtain health information from various sources compared to the male students. Three independent factors of EHIL were found: 1) motivation on finding health information, 2) confidence in one's ability to find, understand, and use health information, and 3) evaluation of health information. This result suggests that these three aspects should be further examined when studying the complex phenomenon of health information literacy and designing measurement tools for practical uses. A shortened 4-item screening tool is presented and proposed for further study and testing as a part of medical interventions, digital library services or modern ICT applications in health education.