When it comes to improving iron-deficient erythropoiesis and boosting the production of new red blood cells, the effects of iron supplements can vary. In cases of severe anemia, it may take a few weeks or even months to notice a significant improvement in symptoms. However, for some individuals, the effects can be felt within a few days. It's important to note that individual responses may differ, and factors like low birth weight in babies can also influence the time it takes to see noticeable benefits. If you have concerns about your progress, consult with your healthcare provider for guidance.