Blood and blood flow play an essential role in the functioning of the human organism in health and disease. In particular, the cessation of bleeding after an injury (hemostasis), the formation of vascular plaques (thrombosis), and the flow disturbance after vascular alterations (aneurysms) or medical interventions (stents) are important conditions, where sophisticated simulations can significantly contribute to the improvement of treatment options. A major challenge for understanding and predicting such conditions is the tight coupling of various processes at the molecular and cellular level with the macroscopic flows in small and large blood vessels. No single simulation technique is able to cover the range of length scales from tens of nanometers to centimeters such that a combination of different approaches is urgently required. In this talk, we present simulations of the macroscopic blood flow dynamics. Here, we use sophisticated non-Newtonian constitutive equations to model the blood flow. These are integrated into our in-house FEM solver FEDDLIB (Finite Element and Domain Decomposition Library). The FEDDLIB is a C++ library, which was originally developed for efficient large-scale simulations together with the highly scalable implicit domain decomposition solver FROSch (Fast and Robust Overlapping Schwarz). This will also enable efficient multiscale simulations in the future.