This paper presents a novel readout circuit with potentiostat for amperometric chemical sensors that has wide output current range and has low power consumption, with its application towards the implantable glucose sensing system. This new design of electrochemical interface circuit operates in current-to-current transfer mode, has low input impedance characteristic and has stable loop gain unaffected by sensor resistance variation. Post layout simulations showed detection of redox current from 50 pA to 50 μA with power consumption from only 390 μW to 745 μW, while experimental verification using on-board prototype provided measurements from 10 nA to 50 μA, with 10 nA as the lowest capability of the semiconductor device analyzer used in the setup. This novel readout circuit was implemented using TSMC 0.35 μm mixed-signal 2P4M 3.3 V CMOS technology with a chip area of 0.1767 mm2.