In this paper, I narrate the history of a burgeoning blood market in Iran between the 1940s and 1970s which operated semi-formally. At the dawn of the twentieth century, the Iranian nation-state had widely adopted Western modes of knowledge-production and technological know-how. Within this context, the Iranian medical society had become familiarized with and depended on the practice of blood transfusion. Yet, whereas the medical expertise and transfusion infrastructure had been built up the early 30s, it was not easy to sustain the required blood for transfusion. The potential blood-givers declined to contribute their blood for the sake of transfusion. To overcome this gap, institutions tried various strategies and mobilized different channels to encourage blood donation. However, none of these strategies fully yielded success. A semi-formal market provided the main portion of the needed blood. Professional blood-sellers and blood-dealers managed and regulated the market. The institutions unwillingly, but inevitably had to rely on the commercialized blood. The blood sellers were usually poor and in need of quick cash. Newly-arrived migrants from rural areas and drug addicts in need of fast money constituted the two major groups among blood sellers. Struggling with poverty, sellers could thus turn their blood, a commodity with relative sustainability, into cash. The existing literature suggests that the modernizing Iranian state in the twentieth century successfully instituted medical regulations such as immunizations, public hygiene, and reproductive health. Nonetheless, the case of blood transfusion suggests that state efforts initially failed to establish a functional blood transfusion system. I argue that the blood transfusion project initially faced difficulties because it depended on the willing participation of the nation. The state needed its citizens to provide its medical institutions with the essential matter of blood. For almost four decades, the ordinary citizens eluded to give away their blood for free to the state institutions. My paper explains how this reluctance charged the state with desperation, while simultaneously creating an opportunity for the poor to sustain their lives through selling their blood in an informal market.