This chapter explores in detail aspects of health in children, adults, and older people with severe intellectual disabilities. It reviews why they have higher health needs when compared with the general population. It also identifies the different pattern of physical health needs and the high comorbidity in this group of people, as well as explores how many health needs can remain untreated. It demonstrates that the health profile of people with mild intellectual disabilities is similar to the wider population, once socio-economic factors are taken into account, although importantly they may experience more difficulty in accessing health promotion and primary and secondary care services. As a result of these factors, which include unmet health needs, many people die unnecessarily and at a premature age. This chapter uniquely provides comprehensive coverage of the very many factors compromising health and well-being, along with providing a range of strategies that registered nurses for people with intellectual disabilities can adopt in order to support health and well-being.