This paper provides a comprehensive review of power management circuit techniques for millimeter-scale biomedical sensing systems, which operate under strict power and energy constraints. It begins by introducing a miniature sensing platform and outlining the key challenges associated with limited energy availability in such ultra-small devices. The discussion then highlights advances in circuit design for efficient power conversion, battery management, ambient energy harvesting, and wireless power transfer. By examining these techniques, the paper aims to clarify the major design challenges and emerging solutions that are driving the development of next-generation miniature biomedical electronics.