In this brief, a fully integrated inverting voltage converter for biasing complementary metal-oxide-semiconductor integrated single-photon avalanche diodes is presented. The design uses a dual-chain inverting Dickson charge pump architecture to generate a negative high voltage output from a single positive supply with a voltage gain factor larger than five, reaching a peak conversion efficiency of up to 20%. A closed-loop controller is implemented for output stabilization. At a set output voltage of -18V for the used diodes, a maximum output power of 500μW with a conversion efficiency of 18% can be achieved. Relying solely on metal sandwich capacitors, the design is resilient to continuous negative high voltage effects and can be used in medical implantable devices requiring long-term reliability. Due to the full integration of all components, it is suitable for low-power implantable medical systems and paves the way towards fully integrated, implanted in-body sensing systems using single-photon avalanche diodes that require negative high voltage biasing. This opens up new fields for uses of high precision and fluorescence imaging in portable devices, not limited to medical devices.