What is the initial workup and treatment for anemia?

Initial Workup and Treatment for Anemia

Begin with a complete blood count (CBC) with red cell indices, reticulocyte count, iron studies (serum ferritin, transferrin saturation, total iron-binding capacity), and inflammatory markers (C-reactive protein) as your essential first-line diagnostic panel. 1, 2, 3

Diagnostic Definitions

• Anemia is defined as hemoglobin < 13 g/dL in men, < 12 g/dL in non-pregnant women, and < 11 g/dL in pregnant women. 1, 2, 3

Morphologic Classification and Interpretation

Microcytic Anemia (MCV < 80 fL):

• Most commonly indicates iron deficiency anemia, but also consider thalassemia, anemia of chronic disease, or sideroblastic anemia. 1, 2, 3
• Confirm iron deficiency with serum ferritin < 30 μg/L and transferrin saturation < 15%. 1, 2, 3
• Even with normal MCV, low MCHC suggests hypochromia and often accompanies early iron deficiency. 2

Normocytic Anemia (MCV 80-100 fL):

• May indicate acute hemorrhage, hemolysis, anemia of chronic inflammation, or early iron deficiency. 2, 3
• Elevated RDW with normal MCV suggests mixed nutritional deficiencies or early iron deficiency. 2

Macrocytic Anemia (MCV > 100 fL):

• May indicate vitamin B12 or folate deficiency, medications, alcohol use, or myelodysplastic syndrome. 2, 3
• Measure vitamin B12 and folate levels to confirm suspected deficiencies. 2

Reticulocyte Count Interpretation

• A low or normal reticulocyte count indicates impaired erythropoiesis (production problem). 2, 3
• An elevated reticulocyte count suggests increased red cell production in response to blood loss or hemolysis. 2, 3
• If hemolysis is suspected, measure haptoglobin, LDH, and bilirubin. 2

Treatment by Etiology

Iron Deficiency Anemia:

• Oral iron supplementation is first-line treatment, with parenteral iron reserved for patients who cannot tolerate or absorb oral preparations. 1
• In adult men and postmenopausal women, always investigate for gastrointestinal blood loss as the underlying cause. 2, 4

Vitamin B12 Deficiency (Pernicious Anemia):

• Administer 100 mcg cyanocobalamin by intramuscular or deep subcutaneous injection daily for 6-7 days. 5
• If clinical improvement and reticulocyte response occur, give the same dose on alternate days for seven doses, then every 3-4 days for another 2-3 weeks. 5
• Maintenance therapy is 100 mcg monthly for life. 5
• Avoid the intravenous route as almost all vitamin will be lost in urine. 5

Folate Deficiency:

• Treat with oral folate supplementation. 1, 2
• Critical caveat: High-dose folic acid may mask B12 deficiency symptoms, so always check B12 levels before initiating folate therapy alone. 1, 2

Anemia of Chronic Disease/Inflammation:

• Primary treatment involves addressing the underlying condition. 2, 3
• Erythropoietin therapy may be considered in specific situations such as chronic kidney disease. 2

Anemia in Chronic Kidney Disease

• Monitor hemoglobin at least every three months in patients with GFR < 30 mL/min/1.73 m². 1, 3
• Initiate workup if hemoglobin < 12 g/dL in women or < 13 g/dL in men. 1, 3
• Treat identified iron deficiency first; if anemia persists despite iron therapy, initiate erythropoietin or analogue therapy. 1, 3
• Measuring serum erythropoietin levels is usually not indicated in chronic kidney disease patients with normochromic, normocytic anemia. 1

Critical Pitfalls to Avoid

• Never assume anemia is "normal aging" in elderly patients—always investigate the cause. 1, 3
• Watch for combined deficiencies, especially in elderly patients and those with inflammatory bowel disease. 1, 3
• In patients with inflammatory conditions, serum ferritin may be falsely elevated due to its role as an acute phase reactant; use ferritin < 30 μg/L as the diagnostic threshold without inflammation. 2, 3
• Always assess for potential sources of blood loss, as iron deficiency in adults often indicates ongoing blood loss requiring gastrointestinal evaluation. 2