The ability of the Lattice Boltzmann method, as the fluid dynamics solver, to properly simulate macroscopic Navies slip boundary condition is investigated. An approximate equation relating the Lattice Boltzmann variable slip boundary condition with the macroscopic Navier's slip boundary condition is proposed. The proposed relation is validated both for the case of Newtonian and non-Newtonian fluids. The importance of employing the Navier's slip boundary condition is highlighted by a practical industrial problem. (C) 2013 Elsevier B.V. All rights reserved.