Previous studies have attempted to develop measurement tools for constitutional identification in Traditional Tibetan Medicine (TTM), but they have limitations. We developed a new constitution self-assessment tool that is more firmly grounded in the Gyüzhi, the foundational text of Tibetan Medicine. This new self-assessment tool takes the form of a questionnaire in which the items represent the diagnostic criteria of the three central elemental dynamics of Tibetan medicine (rLung, Tripa, Béken) and are related to the body, psychology, and diet preferences. We tested versions of the new questionnaire in three samples of Tibetan adults (total n=973) in Qinghai Province and evaluated its validity in 90 respondents randomly selected from the main samples. These respondents completed the questionnaire and were independently evaluated by Tibetan Medicine experts using traditional methods of constitution identification. A comparison of the results led us to revise the original questionnaire. Based on expert advice, we combined similar and overlapping items to simplify and improve the scale. Cronbach's alpha was used to assess internal consistency and indicated that the final scale is reliable. There was 80-93% agreement between experts’ identifications and self-assessment responses in the survey when both types of data were available. The Traditional Tibetan Medicine (TTM) constitution scale developed in this paper has a strong basis in theory and TTM practice. It can be used by Tibetan medical practitioners, other health care providers, researchers, and the lay public to identify individual constitution and help determine appropriate treatment.