A non-sterile medium designed to be applied to a patient's unbroken skin surface to provide a coupling between an analytical device (e.g., ultrasound transducer, optical glucose monitoring system) and the patient, allowing for the emission and reception of signals (e.g., ultrasound, light) that pass through the skin during an examination. It is in the form of a non-sticky, fluid-like gel that may also assists the operator's ability to move the analytical device smoothly over the skin to better analyse the site of interest. It may be used by a healthcare professional or layperson. After application, this device cannot be reused.