Mature erythrocytes are traditionally regarded as anucleate cells lacking nuclear DNA. However, evidence shows they retain residual genetic material, including mitochondrial DNA (mtDNA) and RNA fragments. This review explores the role of such genetic material in cellular function, diagnostics, and erythropoiesis. A comprehensive literature review was conducted, focusing on (i) erythropoiesis, (ii) enucleation of erythroid precursors, (iii) the presence of DNA in red blood cells (RBCs), and (iv) RNA fragments such as messenger RNA (mRNA), microRNA (miRNA), and other non-coding RNAs. Mature RBCs harbor small amounts of DNA and diverse RNA species. Residual DNA can act as damage-associated molecular patterns (DAMPs), triggering immune responses when released under stress or injury. RNA fragments reflect the transcriptional activity of precursor cells and have been linked to potential diagnostic applications. Studies suggest that RBC-derived RNA signatures may serve as non-invasive biomarkers for diseases such as diabetes, cardiovascular conditions, and hematological disorders. These profiles mirror changes in erythropoiesis and provide insights into systemic pathophysiology. Residual genetic material in RBCs extends their role beyond oxygen transport. It contributes to immune modulation and may provide novel diagnostic and therapeutic opportunities, enhancing disease detection and understanding of erythropoiesis.