This chapter critically examines the development and application of impaired life annuities within the UK insurance sector, integrating historical analysis with contemporary actuarial and medical underwriting practices. The evolution from conventional annuity pricing—predicated on limited demographic factors—to advanced, multifactorial risk assessment models is explored, with particular attention to the incorporation of medical, lifestyle, and socioeconomic variables in mortality estimation. Actuarial frameworks for base mortality rates and condition-specific loadings are analyzed, alongside the implications of anti-selection and the operational challenges faced by medical underwriters in quantifying longevity risk. The chapter provides a detailed review of underwriting methodologies for major medical conditions, including cancer, heart failure, chronic respiratory diseases, neurological disorders, and stroke, highlighting the interplay between clinical progression, medical disclosure, and actuarial modeling. The discussion synthesizes recent advances in medical science and their impact on mortality trends, advocating for ongoing refinement of underwriting protocols to enhance fairness and sustainability in annuity pricing. This work contributes to the academic discourse on risk stratification, longevity modeling, and the intersection of medical and actuarial science in insurance product design.