Proactive geosteering involves having deep reading LWD measurements sensible to the surrounding formation and software for processing upcoming data in real-time. Electromagnetic (EM) measurements or resistivity measurements obtained from LWD EM tools contain sufficient information and are widely used in proactive geosteering. The iterative process of running forward modelling computations in order to obtain model parameters which are matching the real-time resistivity measurements is called deterministic inversion. Deterministic inversion method requires significant computing power and may result in slow performance on geosteering engineers' laptops. This paper proposes to use unconventional approach to inversion (linearized inversion) that uses linear approximation of forward modeling in horizontally-layered formation based on modified Born and Doll approximation. Application of linearized inversion approach shows good performance and reliable results for real-time proactive geosteering.