Monitoring in real time: Continuous monitoring of physiological data and vital signs is made feasible by implantable medical devices (IMDs), which may help identify medical issues early and take appropriate action. Implantable antennas are typically designed to operate in medical frequency bands such as the Medical Implant Communication Service (MICS, 402–405 MHz), the Industrial, Scientific, and Medical (ISM) band (2.4 GHz, 5 GHz), and Ultra-Wideband (UWB, 3.1–10.6 GHz), depending on the application. These antennas eliminate the need for regular doctor visits and intrusive tests, making operations less invasive and more comfortable for patients. In this chapter, design and analysis of small size implantable antenna working at 6 GHz have been illustrated. The antenna element is designed with microstrip line on RT Duroid 5880 substrate having dielectric constant of 2.2, a tangent value of 0.0009, a thickness of 0.8 mm, and partial ground. The upper surface of the antenna forms a shape radiator excited via a 50-ohm microstrip feed line and partial ground plane acting as defective ground surface (DGS). DGS acts as a reflector to disturb the flow of surface current distribution on the ground plane with increased isolation and shift to impedance bandwidth range within its resonant band expands. The proposed antenna shows acceptable SAR (1 g) distribution at 6 GHz. The proposed antenna is compact in size and occupies 80 mm3 (10 mm × 10 mm × 0.8 mm).