Systems and methods for determining the yield stress of a non-Newtonian fluid in real time are provided. A pressure loss and/or liquid rise technique, an ultrasonic technique, and/or a penetrometer technique can be used to determine the yield stress of a non-Newtonian fluid. The ultrasonic technique can include a longitudinal wave approach and/or a shear wave approach. The methods and systems are non-invasive and only require slight modifications to the piping containing the non-Newtonian fluid in order to measure the yield stress.