In this work, we demonstrate a wearable tattoo based iontophoretic biosensing system for non-invasive metabolite monitoring application. The epidermal sensor device includes an iontophoretic biosensing temporary tattoo system with flexible wireless electronics. The wearable prototype allows noninvasive biofluid sampling via iontophoresis and amperometric detection of metabolite using enzyme and Prussian blue transducer. On-body results with human subjects show distinct differences in the current response reflecting blood metabolite concentration. The data was transmitted wirelessly in real time via Bluetooth communication. The new wireless epidermal iontophoretic-biosensing system offers considerable promise for noninvasive metabolite monitoring in practical settings and can be readily expanded toward the monitoring of additional analytes.