A complete description of the response of man to large doses of glucose involves the use of more than sixteen rate constants, each varying from one person to the next. It is demonstrated here that the response of blood-glucose concentration (G) as a function of time (t) can be represented adequately by an equation involving only four constants in the equation: G=G0+A e−αt sin ωt. The values of these four constants are defined by the four measurements usually made in an ordinary glucose-tolerance test. The natural frequency ω0=r(ω2 + α2) is shown to represent the product of the rate constants for insulin production due to added glucose and for glucose utilization due to insulin action. On the basis of measurements on over 750 persons, it is suggested that the value of ω0 can be used to distinguish normal from diabetic persons more closely than any other parameter.