Abstract: Glymetrix designs games that front end software that helps people manage diabetes. To do this effectively we base our designs on well articulated theory. Theories of learning styles, of self efficacy, and of needs all underscore the design of the games. Medical evidence is also a critical part of good design when a game is part of a therapeutic application. Research into diabetes care, the effect of gambling on the brain, nutrition, diet and exercise all influence design. This talk will look at Glymetrix general approach to theory and evidence, and go in depth on one or two examples.