The pharmaceutical industry is significantly more carbon intensive than many other industries, such as automobile manufacturing [1]. Furthermore, with pharmaceuticals representing approximately 25% of the carbon emissions associated with the NHS [2], medicines provide an excellent opportunity for carbon reduction. The chemical synthesis of medicines often requires expensive reagents, catalysts with a high embodied carbon content or low relative abundance (e.g., precious metals and rare earths) and high temperatures/pressures, all necessitating high consumption of energy, therefore producing a lot of carbon. Biological processes, however, require lower temperatures (often 37 ⁰C) and removes the need for expensive and unsustainable catalysts. Bioreactors are already used to make products such as insulin, however, many medicines have complex synthesis pathways, and are not currently found in nature. Synthetic biology provides the molecular toolkit to build up modular biochemical pathways, insert them into host organisms to generate chemical compounds through biosynthesis. Once a biochemical pathway is complete within a host organism (for example E. coli), the desired product can be made biologically. Furthermore, biosynthetic pathways can use renewable feedstocks in place of fossil fuel feedstocks, and even sequester carbon when using photosynthetic organisms. This article explores how medicines can be made using biosynthesis, how synthetic biology enables more medicines to be made through biosynthesis, and how this can all be achieved with an exceptionally low carbon footprint.