The National Health Insurance Scheme (NHIS) was established to reduce catastrophic health expenditures and promote universal health coverage (UHC) in Nigeria. Despite its aims, low enrolment and structural fragmentation continue to hinder comprehensive risk pooling. This study critically assesses NHIS’s effectiveness as a social security mechanism by examining its tangible achievements, identifying ongoing operational challenges, and highlighting key policy gaps. Based on Expected Utility Theory (EUT), the research used a focused narrative synthesis of empirical studies, qualitative research, and policy documents published from 2020 to 2025. The data analysis employed a thematic synthesis to integrate findings related to achievements, barriers, and structural issues across various study designs and regions. The synthesis reveals that the NHIS provides substantial financial protection for formal-sector workers and enhances maternal service utilisation among beneficiaries. However, the national impact remains limited by the structural exclusion of the informal sector and the severe fragmentation of risk pools, resulting in inadequate financial protection and persistent high out-of-pocket expenditures nationwide. In conclusion, the NHIS has yet to reach its full potential as a comprehensive social security system. To attain UHC, the government must adopt a unified strategy focused on increasing public funding and merging fragmented risk pools. Recommendations include reforming regulatory frameworks, modernising payment systems, and implementing targeted enrolment strategies for the informal sector.

National Health Insurance Scheme (NHIS), Social Security, Universal Health Coverage (UHC)

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