The most important function of red blood cells (RBCs) is the carrying of oxygen, but they are also involved in inflammatory processes and during coagulation. RBCs are extremely deformable and elastic, as they are exposed to shear forces as they travel through the vascular system. In inflammatory conditions, and in the presence of hydroxyl radicals, RBCs loose their discoid shape. Here, ultrastructure of RBCs is studied using a scanning electron microscope, and we determine how fast changes in healthy individuals are noted after exposure to iron and glucose. We compare shape changes in these experiments to RBCs from diabetic and hemochromatosis patients (wild type, as well as hereditary hemochromatosis with mutations H63D/H63D, C282Y/C282Y, H63D/C282Y, C282Y/wild type and H63D/wild type). Thrombin is also added to whole blood exposed to iron, glucose and blood from diabetes and hemochromatosis patients. RBCs are easily deformed to a pointed shape in smears, and, with the addition of thrombin they are entrapped in the fibrin mesh of dense matted fibrin deposits. This entrapping causes severe shape changes due to the pressure of the fibrin onto the stressed cells. The most important observation of the current research is therefore how fast RBC can adapt in a changed environment and that the pressure of fibrin fibers may trap the RBC tightly in the resulting clot.