Biosensing through bodily fluids (especially through blood) is gaining attention due to their preciseness and broad range of detection. Various point-of-care diagnostic methods based on different sensing techniques are emerging rapidly. However, the future lies in simple and rapid detection technologies with a wide range of applications. Here, we designed a sensor based on microwave spoof surface plasmon polaritons (SSPPs) for sensing biological fluids. A novel octagon-shaped unit cell for the SSPP structure is fully explored in terms of its behavior and sensing capabilities. The SSPP microwave structure with a microfluidic reservoir is built as a multilayer arrangement based on the proposed unit cell to serve as a sensing platform for various bodily fluids. We first evaluated the sensing feature of the designed sensor using various sugar solutions. We further demonstrated the biosensing capacity of the sensor by testing the blood phantom samples, which are prepared with different sugar concentrations. The sensor shows good sensitivity, and the corresponding sensing performance is experimentally validated with the distinguishable resonance frequency shift of 1.202 GHz on average per blood phantom sample. Our analysis revealed that this SSPP-based sensor is a good candidate for biosensing of bodily fluids. This biosensing capability of the sensor may be further extended to other bodily fluids and, thus, offers nondestructive, noninvasive, label-free, rapid, and real-time biosensing.