<p>Biodegradable implantable and wearable biomedical sensors have attracted growing attention as a promising alternative to conventional permanent electronic devices, offering transient functionality that eliminates the need for secondary surgical removal and mitigates electronic waste accumulation. Among various sensing modalities, capacitive sensors have emerged as a particularly attractive platform for monitoring mechanically derived physiological signals owing to their structural simplicity, low power consumption, and compatibility with soft materials. Despite extensive academic progress, however, the clinical translation and commercialization of biodegradable capacitive sensors remain limited. A central challenge arises from the inherent trade-off between sensing sensitivity and operational lifetime. Structural and material modifications that enhance sensitivity often accelerate degradation, whereas strategies designed to prolong functional lifetime can compromise mechanical compliance and signal fidelity. Achieving a precise balance between these competing requirements is therefore critical for practical deployment in biomedical applications. In this review, we systematically examine biodegradable capacitive sensors with a focus on sensitivity enhancement and lifetime modulation as the two key determinants of device performance. We summarize design strategies for improving sensitivity through sensor architecture optimization and dielectric layer engineering, and we review encapsulation approaches for controlling degradation behavior and functional lifetime. By critically analyzing how these complementary strategies are selectively implemented to meet the distinct demands of wearable and implantable biomedical applications, this review provides practical design guidelines and highlights future research directions aimed at advancing biodegradable capacitive sensors toward clinical implementation and scalable manufacturing.</p>