The study focuses on the behavior of diffusion phenomenon in the normal and stenosed capillary-tissue exchange system where the rheology of flowing blood in the capillary is characterized by the generalized Bingham Plastic fluid model. Assessment of the severity of the disease could be made possible through the variation of a parameter named as retention parameter. The concentration profile and associated physiological diffusion variable involved in the study for normal and diseased state have been analyzed. The model is also employed to study the effect of shape of stenosis on flow characteristics. An extensive quantitative analysis is performed through numerical computations of the desired quantities having physiological relevance through their graphical representations so as to validate the applicability of the present model.