A cost-effective noninvasive 2.4 GHz microwave blood glucose sensor is designed and implemented in this study. The special feature of the system is that it can operate independently without any other equipment, and the system is small in size and easy to carry. When the system is powered on and the ring finger is placed on the sensor, the blood glucose level (BGL) can be determined. The system is easy to operate and can be used continuously. For the system, a special sensor element with metamaterial cells and a specific RF-DC rectifier circuit are designed and implemented. An algorithm that can calculate BGL from the sensing voltage generated by detecting the fingertip and programmed to run in the embedded system is developed. Compared with BGL detected by a commercially available invasive blood glucose sensor, the detection error of the proposed sensor is less than 2%. The proposed noninvasive 2.4 GHz microwave blood glucose sensor is very simple and inexpensive, and the measurement results are very close to those of commercially available sensors.