In recent years, the oil & gas industry has adopted the use of High Viscosity Friction Reducers (HVFR) in fracturing fluids since they present several advantages over traditional systems based on guar gum. One of the most significant advantages is their ability to provide pipe friction reduction during fracturing treatment. It allows to increase flowrate while maintaining fracturing pressure and, thus, reducing pumping time. It has made possible to increase the fractures stages performed per day impacting strongly on completion costs. However, there is a lack of knowledge on how to characterize these fluids in laboratory and on how their properties affect their performance on field. The main purpose of this paper is to understand of rheological properties of HVFR fracturing fluids and to develop a method to establish the most efficient polymer concentrations in fracture designs considering different water salinities. The steady shear viscosity profile was measured under a wide variety of polymer concentrations across a range of shear conditions. The correlation between zero shear viscosities and polymer concentration allows to differentiate between Slickwater, MVFR (Medium Viscosity Reducer) and HVFR regimes. These results were used to optimize treatment designs: polymer and sand addition schedules; reducing the total volume of polymer consumed per fracture stage.