Iron-deficiency anemia (IDA) is a global health concern, and its widespread prevalence and multifaceted impact on various populations, particularly in developing countries, underscore the urgency for efficient diagnostic and management strategies. While traditional diagnostic methods such as ferritin and transferrin saturation are fundamental, their limitations in sensitivity and specificity lead to challenges in the early detection and effective management of IDA. This review provides a comprehensive analysis of IDA, focusing on the evolution of diagnostic methods culminating in the utilization of reticulocyte hemoglobin content (CHr) as a critical biomarker. The core of this review is the detailed examination of CHr as a biomarker. Its emergence has been pivotal due to its superior sensitivity and specificity in identifying iron deficiency and monitoring therapy efficacy. The review discusses the comparative advantages of CHr over conventional methods, including its ability to detect IDA at an earlier stage and its utility in varied demographic groups, such as children and pregnant women. Future research directions are proposed, including integration of CHr into routine clinical practice, cost-effectiveness analysis, and technological advancements for enhanced measurement and accessibility. In conclusion, CHr holds significant potential for revolutionizing IDA management, paving the way for more precise and personalized medical interventions, thereby improving patient outcomes in diverse populations.