In Western countries, blood supply agencies encounter impediments in providing blood groups defined as rare or of interest, notably for sub-Saharan African ancestry (SSAA) recipients. To establish warning levels and anticipate future blood needs, an estimate of the current carriers of rare blood groups, both potential patients or donors, is crucial but complex. Indeed, if the strict needs can be estimated in medical terms, the modalities of blood product collection must be considered from an interdisciplinary perspective, at the interface of biological data and social norms. Here, we aim to understand how legal choices and a set of representations of otherness may influence the supply of rare blood for SSAA populations. After examining these issues, considering different norms and limits that govern French society, we compare this data with those of four Western countries facing the same difficulties (United States, United Kingdom, Italy and the Netherlands). This work began as part as the reflections of Social Lab, an institutional programme created by the French Blood Establishment (EFS). How can we effectively improve the qualitative blood coverage for SSAA populations? There is no unique solution, but there are many more or less effective answers. Comparison across countries reveals a strong influence of the socio-political histories and ethical choices before technical and medical considerations. We consider that an institutional policy is required to resolve recruitment issues of SSAA donors sustainably. Lastly, we introduce a working group called the EFS Social Lab, which aims to set up a monitoring mechanism for donors and societal trends to make blood donation effective.