This paper presents an integrated control circuit and system design for an implantable glucose biosensor. A microcontroller unit (MCU) is configured to work as the core control circuit for the whole system. An 8-bit MCU is chosen due to its low power characteristics. The front-end glucose sensing module utilizes a low-power wide-current-sensing-range readout circuit with a potentiostat for amperometric chemical sensors. Post layout simulations for the readout circuit show a redox current of 50 pA to 50 μA with a power consumption of 390 μW to 745 μW. A closed-loop insulin delivery system is integrated with the implanted module, which is controlled by the MCU. A power management chip which includes the closed-loop insulin delivery system is developed to meet the power requirements of implantable systems. The power management chip is fabricated in TSMC 0.35-μm 2P4M 3.3/5 V CMOS technology. It occupies an area of 2.382 × 2.374 mm2 (core size = 2.200 × 1.086 mm2) and dissipates 36.3 mW of power. An in-depth analysis of the proposed system is undertaken. The experimental results match those of the circuit simulations.