Real-time and multi-target detection by wireless implantable devices is of increasing interest for chronic patients. In this work, electrode sharing is proposed to minimize the size of the implantable device when several three-electrode-based sensing sites are needed. An integrated potentiostat and readout circuit for a multi-target biosensor is presented. To realize this, the circuit reads out the sensor current through each working electrode in a current-mode scheme. The maximum detectable current is 8 μA and the simulated input referred current noise of the circuit is 125 pA/pHz at 1 Hz. The circuit was fabricated in 0.18 μm technology and tested for two lactate biosensors fabricated with a commercial lactate oxidase and an engineered one. Chronoamperometry experiments performed with the circuit agree well with a commercial equipment for lactate detection up to 1 mM.