In this paper, we have presented a novel plasmonic Refractive Index (RI) sensing scheme based on a rewritable optical disc structure with customized dimer-like nanopatterns. We have performed the finite-difference time-domain (FDTD) simulation for this work to exhibit the optical resonant response and sensing performance of our proposed sensing platform. We have also investigated how the changes in the different structural parameters affect the resonant wavelength. The high refractive index sensitivity of 768nm/RIU allowed our sensing system to achieve a resolution limit for blood Hemoglobin(Hb) detection superior to most Hb sensors previously reported. The use of the built-in grating structure of the optical disc, the ability to create customized patterns, and the high resolution achieved in blood Hb detection suggest the potential of our proposed RI sensor as a cost-efficient, reliable sensing technology for medical applications.