This study investigates the risk of anemia development in women aged 18-55 years with non-anemic iron deficiency and evaluates the clinical effects of oral iron therapy. The study consists of a two-month nutritional intervention phase followed by a one-month oral iron treatment phase. Participants first receive dietary counseling aimed at increasing iron intake and absorption. After two months, changes in hematologic parameters and symptoms are evaluated. Women with persistent iron deficiency then receive daily oral ferrous sulfate (80 mg elemental iron) for one month. The study aims to identify early predictors of anemia progression and to assess the impact of dietary modification and oral iron therapy on symptoms and laboratory findings.

This study examines the risk of anemia development in women aged 18-55 years with non-anemic iron deficiency (NAID) and evaluates the clinical effects of oral iron therapy in those with persistent deficiency. The objective is to characterize individual and clinical factors associated with progression toward anemia and to assess the impact of nutritional modification and subsequent iron supplementation on hematologic and symptom-based outcomes.

Iron deficiency is one of the most common nutritional deficiencies globally. NAID often remains unrecognized despite its potential to cause fatigue, decreased physical performance, and progression to anemia if untreated. Iron plays a key role in oxygen transport, DNA synthesis, and muscle metabolism. Dietary intake includes both heme (animal-derived) and non-heme (plant-derived) forms with differing bioavailability. Ferritin is the primary biomarker used to diagnose iron deficiency, though inflammatory conditions may influence its accuracy. A careful differential evaluation is important to distinguish NAID from other causes of anemia such as chronic disease, B12 or folate deficiency, thalassemia syndromes, thyroid disorders, or gastrointestinal blood loss.

The study uses a two-phase, single-center prospective design at Kağıthane 5 No'lu Family Health Center (ASM), Istanbul, Turkey, conducted under ethics committee approval and institutional permission. In the initial two-month observational phase, participants receive standardized dietary counseling aimed at increasing iron intake and improving absorption. Health status and adherence are monitored biweekly. After this period, participants are categorized into four groups according to hematologic changes: isolated iron deficiency; microcytosis/hypochromia with minimal hemoglobin decline (<1 g/dL) ; greater hemoglobin decline without meeting anemia thresholds; or overt iron deficiency anemia.

In the subsequent one-month experimental phase, participants with persistent deficiency receive oral ferrous sulfate providing 80 mg elemental iron daily. Clinical and laboratory evaluations are performed at designated time points to assess changes in complete blood count parameters, ferritin, serum iron indices, inflammatory markers, and patient-reported symptoms.

Primary outcomes include changes in symptom scores, while secondary outcomes evaluate hematologic and biochemical responses. Planned analyses explore associations between baseline characteristics, dietary habits, and anemia progression. Power analysis using repeated measures ANOVA indicated a required sample size of 60 participants.

This research highlights the importance of individualized management strategies for iron deficiency, aiming to support appropriate use of supplementation while reducing unnecessary treatment and potential adverse effects. Enhancing dietary iron intake may help prevent anemia progression, promote patient safety, and improve resource utilization in primary care settings.

Inclusion Criteria:

• Female participants aged 18-55 years (including premenopausal and menopausal women).
• Normal hemoglobin level (≥ 12 g/dL).
• Serum ferritin < 15 μg/L (WHO criteria for iron deficiency).
• Mentzer index > 13.
• Normal levels of vitamin B12, folic acid, thyroid hormones (TSH and sT4), and C-reactive protein (CRP < 5 mg/L).
• Non-anemic iron deficiency confirmed by laboratory results.
• Good general health and cognitive capacity to provide informed consent.
• Willingness to participate, comply with study procedures, and provide written informed consent.

Exclusion Criteria:

• Pregnancy or postpartum period.
• Acute or chronic infections.
• History or suspicion of malignancy.
• Chronic inflammatory or autoimmune diseases.
• Chronic fatigue syndrome or depressive disorders.
• Chronic kidney disease or renal failure (acute or chronic).
• Congestive heart failure, ischemic heart disease, or cerebrovascular disease.
• Coagulopathy or clinically significant bleeding tendency.
• Hematological disorders (e.g., thalassemia, hemoglobinopathies).
• Postoperative patients, transplant recipients, or dialysis patients.
• Currently using any form of iron supplementation or treatment.
• Any condition that, in the investigator's opinion, may interfere with the participant's safety or the interpretation of study results.

No parties are masked; this is an open-label study.