Low literacy is an important and widespread problem. Deficiencies in basic reading, communicating, and comprehension skills significantly affect the ability to function in daily life, particularly effective use of medicines, as patients cannot perform necessary functions in health care environment such as understanding the directions on the label on medication packages [1]. In 1990, the UNESCO reported 26.6 % of adults in the world were illiterate and of those 34.9 % were in developing countries [2]. Illiteracy rate was found quite high (30 %) in Asia, whereas it was as low as 1 % in developed countries [3]. In Thailand, the report of literacy survey illustrated that Thai people were approximately 95 % literate [4]. The Thai National Statistical Institute reported more than 7.5 % of Thai people over the age of 50 were illiterate [5]. Level of literacy has an impact on health literacy, which means the cognitive and social skills of individuals to gain access to understand and use promoted health information for maintaining good health [6]. Inadequate health literacy may therefore decrease abilities of people to understand health information. In addition, people with low literacy are likely to have difficulties in understanding language/instruction in medication labels [6,7]. This problem results in poor health outcomes and high healthcare costs [8-10]. Previous studies reported that abilities to read [11,12] and understand medication [13] labels are important to medication adherence. One way to facilitate communication of medication information with patients, who literacy skills are limited, is to incorporate visual aids; such as graphic symbols or pictograms, on medication labels and leaflets [14] .