IDDSI tests are easy to use, inexpensive and widely available thanks to the use of syringes, forks and spoons. The aim of this study is to propose a model to predict the transient flow during the IDDSI syringe flow test. Unlike previous approaches, the simple theory developed in this study does not require the use of any simulation software, and predicts IDDSI flow test considering the complete flow curve of the fluid, rather than considering arbitrarily the viscosity at a single shear rate.