Given a CBC showing normal white‑blood‑cell count and platelets but mild normocytic anemia (hemoglobin 11.7 g/dL, hematocrit 36.9 %, red‑cell count 4.27 M/µL, MCV 86.4 fL, MCH 27.4 pg, MCHC 31.8 g/dL, RDW 15.5 %), what is the likely etiology and what further evaluation or treatment is recommended?

Mild Normocytic Anemia: Likely Anemia of Chronic Disease/Inflammation

This CBC shows mild normocytic anemia (Hb 11.7 g/dL) with borderline-high RDW (15.5%), most consistent with anemia of chronic disease/inflammation or early nutritional deficiency; the immediate next steps are iron studies (ferritin, transferrin saturation), renal function (creatinine, eGFR), and assessment for chronic inflammatory conditions.

Interpretation of the CBC Pattern

Your patient has:

• Mild anemia (Hb 11.7 g/dL, just below the 12.0 g/dL threshold for women)
• Normocytic indices (MCV 86.4 fL is solidly within normal range)
• Borderline-elevated RDW (15.5%, at the upper limit of normal at 16.0%)
• Normal white cells and platelets (ruling out bone marrow failure or multi-lineage disorders)

The combination of normocytic anemia with normal-to-borderline RDW creates a specific diagnostic pattern. According to the classification scheme using MCV and RDW, this represents "homogeneous normocytic" (HMN) anemia, which is the most common anemia pattern across all age groups, representing 60-76% of anemia cases and is most frequently linked to anemia of chronic disease 1.

Most Likely Etiologies (in Order of Probability)

1. Anemia of Chronic Disease/Inflammation

This is the most common cause of normocytic anemia 2, 3. The anemia of CKD and chronic inflammatory conditions is characteristically normochromic and normocytic 2. Look specifically for:

• Chronic kidney disease (even mild renal impairment)
• Autoimmune conditions (rheumatoid arthritis, lupus, inflammatory bowel disease)
• Chronic infections
• Malignancy

2. Early Iron Deficiency

The borderline-high RDW (15.5%) is a critical clue. Early iron deficiency can present as normocytic anemia before MCV drops, with RDW rising first as the red cell population becomes more heterogeneous 4. The RDW-MCV classification improves detection of early iron deficiency 4.

3. Combined Nutritional Deficiency (Dimorphic Anemia)

Though less common, dimorphic anemia (combined iron and B12/folate deficiency) predominantly presents as microcytic or normocytic, rarely macrocytic 5. The normal MCV can mask dual deficiencies that cancel each other out.

4. Occult Blood Loss

Particularly in women of reproductive age, ongoing menstrual losses or gastrointestinal bleeding can cause normocytic anemia before iron stores are fully depleted.

Algorithmic Workup

First-Line Tests (Order Immediately)

Iron studies are mandatory 2, 6:

• Serum ferritin (assesses iron stores; <30 ng/mL suggests iron deficiency)
• Transferrin saturation (TSAT; <20% indicates inadequate iron for erythropoiesis)
• Note: Ferritin is an acute phase reactant and may be falsely elevated in inflammation

Renal function 2:

• Creatinine and eGFR
• Anemia prevalence increases as kidney function declines, and CKD patients develop anemia at higher eGFR levels than expected 2

Reticulocyte count 2:

• Assesses bone marrow response appropriateness
• Low reticulocyte count with adequate iron/B12/folate suggests erythropoietin deficiency or inflammation 2

Second-Line Tests (Based on Initial Results)

If iron studies are equivocal or ferritin is 30-100 ng/mL (gray zone):

• Vitamin B12 and folate levels (to exclude combined deficiency)
• C-reactive protein (CRP) or ESR (to assess for inflammation)

If renal function is abnormal:

• Consider erythropoietin level (though typically not needed for diagnosis)

If gastrointestinal symptoms or risk factors present:

• Celiac serology (tissue transglutaminase antibodies)
• H. pylori testing if iron deficiency confirmed and GI evaluation planned 6

When to Pursue GI Evaluation

If iron deficiency is confirmed (ferritin <30 ng/mL, TSAT <20%), and the patient is not menstruating or has no obvious blood loss source, pursue GI evaluation 6:

• Upper endoscopy (OGD) and colonoscopy are indicated
• Faecal occult blood testing is not useful in IDA workup—it is insensitive and non-specific 6

Treatment Approach

Iron Replacement (If Iron Deficiency Confirmed)

Oral iron is first-line 6:

• Ferrous sulfate 200 mg twice daily (most cost-effective)
• Lower doses may be equally effective and better tolerated
• Continue for 3 months after correction to replenish stores 6
• Add vitamin C 250-500 mg with iron to enhance absorption 6

Parenteral iron if oral intolerance or non-response 6:

• Iron sucrose (Venofer) 200 mg IV over 10 minutes
• Ferric carboxymaltose (Ferinject) up to 1000 mg over 15 minutes
• Iron dextran carries higher anaphylaxis risk (0.6-0.7%) 6

If Anemia of Chronic Disease/Inflammation

Treat the underlying condition 3. Red blood cell transfusions should be limited to severe symptomatic anemia 3.

For CKD-related anemia 2:

• Erythropoiesis-stimulating agents (ESAs) should not be initiated in asymptomatic patients until Hb <10 g/dL
• Ensure iron sufficiency before starting ESAs

Critical Pitfalls to Avoid

1. Don't assume normocytic = not iron deficiency: Early iron deficiency presents with rising RDW before MCV drops 4

2. Don't skip iron studies: Even with normal MCV, iron deficiency or functional iron deficiency (adequate stores but unavailable for erythropoiesis) is common 2

3. Don't ignore the borderline-high RDW: This suggests red cell heterogeneity and warrants investigation for nutritional deficiency or early hemolysis 1, 4

4. Don't order faecal occult blood tests: They add no value in anemia workup 6

5. Ferritin interpretation requires context: In inflammatory states, ferritin may be normal or elevated despite true iron deficiency; TSAT becomes more important in this setting 2

6. Screen for CKD: Anemia may be the presenting sign of chronic kidney disease, which requires specific management 2