One task in risk assessment of engineered nanoparticles is toxicological studies. A suitable interpretation of these investigations demands a comprehensive physical-chemical characterization. Here, we present an approach to gain well-dispersed nanoparticles in physiological media. Therefore, a step-by-step procedure is demonstrated on two different tungsten carbide nanopowders which can be transferred to other powders. The procedure includes a comprehensive powder characterization, followed by a preparation of a non-physiologic, electrostatically stable nanoparticle suspension and finally closes with investigations of the particles' behavior in different physiological media. Our study showed that the particles agglomerate in protein-free media. In this context, dependencies of mass- and surface-based nanoparticle concentrations as well as of different physiological media were analyzed. In the presence of bovine serum albumin (BSA) or serum, the agglomeration process is decelerated or, at the appropriate protein amount, prevented.