The results presented herein suggest that ferritin levels ≤ 50 ng/mL could be indicative of early iron deficiency, mainly based on the behavior of the sTfR to hepcidin ratio, showing that this threshold could be considered as the clinically relevant cut-off for absolute ferropenia in order to perform an early diagnosis of potential causes and to start specific treatment. This evidence concerns the gene TFRC and nutritional disorder.