A mathematical model for blood flow in narrow capillaries under the effect of transverse magnetic field has been investigated. It is assumed that there is a lubricating layer between red blood cells and tube wall. The transient flow of the fit red blood cell surrounded by plasma annulus in the narrow capillary is considered. The analysis of fluid flow between red cell and tube wall, when the cell appears to be at rest and the capillary wall moving backwards, is made. The effect of transverse magnetic field on the flow is examined. Computational results are shown through graphs to describe the effect of various parameters on velocity profile, leak-back flow rate and skin friction.