This work presents a switchable and tunable dual-band terahertz (THz) metasurface absorber based on vanadium dioxide (VO2), designed for high performance biochemical sensing. The absorber employs a complementary metamaterial geometry consisting of patterned VO2 on a SiO2 substrate with a gold backplane, achieving two narrowband absorption peaks at 4.88THz and 14.80THz with absorption efficiencies of 98.76% and 95.03%, respectively, and polarization insensitivity. Dynamic modulation of VO2 conductivity enables reconfigurable absorption, offering switchable operation between insulating and metallic phases. Parametric analysis confirms strong geometrical tolerance, while sensing studies demonstrate a maximum refractive index sensitivity of 1.65THz/RIU. The device effectively detects biochemical analytes and differentiates malaria-infected red blood cell phases. Furthermore, machine learning-driven regression models were applied for refractive index prediction, with polynomial regression achieving the highest accuracy (R2=0.9809). The proposed design demonstrates compact geometry, dual-band tunability at higher THz frequencies, and enhanced sensitivity, making it a promising platform for biochemical, and biomedical sensing applications.