This work presents a battery-less biosensing system for solar-cell-powered continuous glucose monitoring contact lenses featuring a 2.4 GHz transmitter. The modulation method combines frequency shift keying and pulse interval modulation to send radio frequency signals with two-dimensional information including the solar cell’s voltage, aiming to overcome the impact of unstable solar power. The transmission distance is longer than 40 cm, which allows communication between contact lenses and handsets. The fabricated chip in a 65 nm CMOS process consumes 126 nW at 0.37-V supply, which is manageable by solar cells in an indoor ambient-light environment.