Human blood (blood bank, expired) sheared through stainless steel capillary tubing (508 pm ID) is analyzed for plasma hemoglobin to study the effect of shear-induced blood damage within the low-stress regime (stress 5 20 Pa). Blood damage results are described in terms of capillary length (related to blood residence time) and wall shear rate for assessing bulk and surface effects. A phenomenological model is proposed to explain these experimental results, obtained over a shear rate range to 7,000 s-'.