Diabetic peripheral neuropathy (DPN) is one of the most common complications of diabetes. Proactive treatment options remain limited, largely due to a lack of sensitive and convenient diagnostics, especially early in disease progression or specifically for small fiber neuropathy (SFN), the dying back of distal small diameter nerves. Here, we report on the design, testing, and validation of a novel medical diagnostic device for the functional assessment of small fiber nerves: an electrically conductive needle array designed to record nerve activity signals in the skin and transdermal tissues, which we call the DEN (Detecting Early Neuropathy). DEN recordings were validated across a time course of high fat diet-induced DPN in mice. Based on preclinical mouse data, the device was then adapted to obtain recordings in human tissue. DEN recordings successfully recorded various types of neural activity. New functional diagnostic tools like DEN offer a promising outlook for patients needing an earlier and more sensitive diagnosis of SFN/DPN, which will allow for earlier and more effective treatment options such as implementation of glucose regulation strategies.