A single ascending dose study (SAD study) is a type of Phase I trial. Single ascending dose studies are usually conducted in a small number of healthy volunteers (although some trials recruit patients). The aim is to find out the safe dose range, and to look for any side effects. The initial dose given will be very small and increased gradually (in a new group of volunteers) if no or only mild side effects are seen. Researchers will also take measurements to determine how the medicine is processed in the body.