A swallow challenge medium (10) is thixotropic for easy swallowing and to provide enough viscosity for effective challenge to peristalsis (20) and has high ionic density for effective impedance measurements by contact with electrodes (41 48) positioned in a person's esophagus (E) or oropharynx during swallow testing. The medium (10) also has a high surface tension so as not to adhere to or coat the electrodes (41 48) or probe (12) surfaces. These physical characteristics are stabilized and consistent enough to provide standard for esophageal and/or oropharyngeal function testing and diagnostics.