Anemia Initial Workup and Treatment
Begin with a complete blood count (CBC) with red cell indices, reticulocyte count, iron studies (serum ferritin and transferrin saturation), and inflammatory markers (C-reactive protein) as your essential first-line laboratory evaluation. 1, 2
Diagnostic Thresholds
Anemia is defined as hemoglobin:
These thresholds should trigger immediate workup rather than observation. 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
- Confirm iron deficiency with serum ferritin < 30 μg/L and transferrin saturation < 15-20%. 1, 3
- Low MCHC suggests hypochromia, which often accompanies iron deficiency even when MCV remains normal. 2
Normocytic Anemia (MCV 80-100 fL)
- Check reticulocyte count first to distinguish regenerative from non-regenerative causes. 3
- If reticulocytes > 100 × 10⁹/L, evaluate for hemolysis (measure haptoglobin, LDH, bilirubin) or acute blood loss. 2, 3
- If reticulocytes are low or normal, consider anemia of chronic disease, chronic kidney disease, or bone marrow disorders. 2
- Measure serum creatinine and calculate GFR in all patients with normocytic anemia. 3
Macrocytic Anemia (MCV > 100 fL)
Red Cell Distribution Width (RDW) Interpretation
- Elevated RDW with normal MCV suggests early iron deficiency, mixed nutritional deficiencies, or other causes. 2
- This pattern warrants iron studies even when MCV appears normal. 2
Treatment Algorithms
Iron Deficiency Anemia
- Oral iron supplementation is first-line treatment. 1, 3
- Intravenous iron is indicated for oral iron intolerance, malabsorption, or chronic inflammatory conditions. 3
- In men and postmenopausal women with confirmed iron deficiency (ferritin < 30 μg/L or transferrin saturation < 20%), refer to gastroenterology to rule out gastrointestinal malignancy. 3, 4
Vitamin B12 Deficiency (Pernicious Anemia)
- Administer 100 mcg intramuscular or deep subcutaneous cyanocobalamin daily for 6-7 days. 5
- If clinical improvement and reticulocyte response occur, give the same amount on alternate days for seven doses, then every 3-4 days for another 2-3 weeks. 5
- Maintenance: 100 mcg monthly for life. 1, 5
- Avoid intravenous route as almost all vitamin will be lost in urine. 5
Folate Deficiency
- Treat with oral folate supplementation. 1, 2
- Critical pitfall: High-dose folic acid may mask B12 deficiency symptoms, so always check B12 levels before initiating folate therapy. 1, 2
Anemia of Chronic Disease
- Treat the underlying condition first. 2
- Iron supplementation, folic acid, and vitamin B12 may be needed based on specific deficiencies. 6
- 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
- Initiate workup if hemoglobin < 12 g/dL in women or < 13 g/dL in men. 1
- Treat identified iron deficiency first, and if anemia persists despite iron therapy, initiate erythropoietin or analogue therapy. 1
- If GFR < 30 mL/min/1.73 m², consider nephrology referral. 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
- Watch for combined deficiencies, especially in elderly patients and those with inflammatory bowel disease. 1
- In patients without obvious blood loss, gastrointestinal evaluation may be warranted. 2
- For severe symptomatic anemia with fatigue, dizziness, or hypotension, consider blood transfusion. 2