This study introduces an all-metal based hexagonal terahertz metamaterial absorber designed for biomedical sensing applications. The proposed structure consists of two metallic layers: a steel plate at the bottom and an upper layer comprising four concentric hexagonal ring resonators of same metal. The absorber demonstrates four significant absorption peaks of 94.0%, 99.2%, 93.8%, and 92.6% at resonance frequencies of 2.852 THz, 3.031 THz, 3.352 THz, and 3.784 THz respectively. Notably, the second resonance peak at 3.031 THz is selected for sensing applications due to its maximum absorption efficiency. At this frequency, the proposed absorber exhibits a quality factor of 591.75 and a Figure of Merit of 359.22, both exceptionally high compared to conventional terahertz sensors. The device can effectively detect changes in the refractive index of biological tissues within the range of n=1.30 to 1.40. The Full Width at Half Maximum bandwidth is calculated to be 5.1221 × 10−3 THz, further confirming its suitability for precise biomedical sensing. In addition, the sensitivity of the structure is determined as 1.84 THz/RIU at 3.031 THz, where RIU represents the Refractive Index Unit. The absorption mechanism of the proposed absorber is thoroughly explained through the analysis of current distribution plots. The proposed absorber demonstrates potential applications in terahertz biomedical sensing.