There are number of shear thinning fluids which follows different laws of viscosity i.e. power law model, cross model, carreau model etc. You have to select the viscosity law of your fluid. Blood is a shear thinning fluid and User defined material input file for Blood is attached for your reference. Power law model is used for blood. Hope this will help you.
Thank you Faisal Sir or the help, but I doing with carreau model , do you have anything related to that, Please let me know, it would be really great !!!