What type of anemia does a patient with a Hemoglobin (Hgb) of 9.5, Hematocrit (Hct) of 29.4, Mean Corpuscular Volume (MCV) of 103.9, and low folate level have and why?

Macrocytic Anemia with Elevated Reticulocyte Count

This patient has macrocytic anemia due to reticulocytosis, not vitamin deficiency, as evidenced by the markedly elevated reticulocyte count (29.6) with normal B12 (437) and folate (7.11) levels. 1

Classification and Key Findings

The patient presents with:

• Macrocytic anemia: MCV 103.9 (elevated), Hemoglobin 9.5 g/dL 2
• Elevated reticulocyte count: 29.6 (markedly elevated) 1
• Normal vitamin levels: B12 437 and folate 7.11 exclude megaloblastic causes 3
• Normal hemolysis markers: LDH 187 (normal), haptoglobin 217 (normal), bilirubin <0.2 (normal) 2

Why This is NOT Vitamin Deficiency Anemia

The normal B12 and folate levels definitively exclude megaloblastic anemia as the primary cause. 3 While vitamin B12 and folate deficiency are the most common causes of macrocytic anemia, they present with low or normal reticulocyte counts due to ineffective erythropoiesis, not elevated reticulocyte counts. 3

The reticulocyte count is critical for distinguishing between ineffective erythropoiesis (vitamin deficiency, bone marrow disorders) and increased red cell production (hemolysis, hemorrhage). 1 An elevated reticulocyte count with macrocytosis indicates hemolysis or recent hemorrhage. 1, 3

Why This is Reticulocytosis-Induced Macrocytosis

Reticulocytes are larger than mature red blood cells, and when present in high numbers, they elevate the MCV mechanically. 1 This patient's markedly elevated reticulocyte count (29.6) is sufficient to cause the observed macrocytosis (MCV 103.9). 1

The normal hemolysis markers (LDH, haptoglobin, bilirubin) argue against active hemolysis as the cause of reticulocytosis. 2 This suggests either:

• Recent acute blood loss with appropriate bone marrow response 1
• Recovery phase from a previous anemia 1
• Occult bleeding that requires investigation 2

Iron Status Assessment

The iron studies show:

• Ferritin 94.8: Normal, excluding iron deficiency 2
• Iron 43: Low-normal
• TIBC 187: Low (normal is typically 250-450)
• Transferrin saturation: 23% (calculated: 43/187 × 100), which is borderline low 2

The low TIBC with borderline transferrin saturation suggests possible early iron deficiency or anemia of chronic disease, but the normal ferritin makes significant iron deficiency unlikely. 2 The MCH of 33.6 is normal, which also argues against iron deficiency. 1

Clinical Algorithm

1. Investigate for blood loss: Given the elevated reticulocyte count without evidence of hemolysis, evaluate for gastrointestinal bleeding with stool guaiac testing and consider endoscopy if indicated, as 60-70% of patients with unexplained anemia have a GI source. 4

2. Monitor reticulocyte count: Repeat CBC and reticulocyte count in 2-4 weeks to assess whether this represents recovery from acute blood loss or ongoing hemorrhage. 3

3. Reassess if reticulocytes normalize: If the reticulocyte count normalizes but macrocytosis persists, reconsider other causes including medications, thyroid disease, or bone marrow disorders. 3

Common Pitfalls to Avoid

• Do not treat with B12 or folate supplementation when levels are normal, as this will not address the underlying cause and may delay appropriate diagnosis. 3
• Do not assume macrocytosis always means vitamin deficiency—reticulocytosis is a common and often overlooked cause of elevated MCV. 1
• Do not ignore the reticulocyte count—it is the single most important test for differentiating causes of macrocytic anemia. 1, 3