The demand for humanitarian and development aid has risen to an unprecedented level in recent years. With a pressing need for new solutions, designers have started using digital fabrication (3D printing, CNC milling and laser cutting) to produce life-saving items. However, many organisations are failing to create the impacts they desire, and the social aspect of sustainability has been largely overlooked. This paper addresses this gap in knowledge by investigating guidelines for Design for Social Sustainability, specifically looking at digital fabrication for humanitarian and development projects. Building on existing literature and conducting three in-depth case studies of healthcare related products, the research develops a framework for Design for Social Sustainability. It provides useful guidelines to help plan and evaluate digital fabrication projects in the humanitarian and development sector. The findings show how design can trigger social sustainability at product, process and paradigm levels. Specifically, the case studies reveal the potential for digital fabrication to lead to more systems-focused, radical social sustainability. The paper concludes that an iterative and holistic approach to Design for Sustainability is needed, that begins by examining the social dimension first.