This study aimed to design, develop, and evaluate efficiency of a human-based “U-Blood App” prototype for blood unavailability in Thailand. This study adopted a mixed-method design. The results of the study revealed these key findings. First, the needs analysis of 32 key informants (50% males and a mean age of 40.6 years) indicated that the features of the User Experience (UE) and the User Interface (UI) should contain blood donor’s qualification, general information record of the blood donor’s health, blood donation appointment and notification schedule, the application download and installation, a simple guide for the application user, the hospital logo, and necessary information. Second, the evaluation by experts revealed that the quality of the prototype is high (X¯=4.79) and the quality of UI ( X¯=4.79) was higher than that of UE (X¯=4.70). Lastly, the end users of 65 samples (50.76\% females and a mean age of 48 years) are highly satisfied with the prototype (X¯=4.68). The findings advanced the understanding of the impacts of human factors on the development of smart phone application for blood donation. The overall results cannot be generalized in the long term. Future inquiry should work on this limitation.