Platelet Count in Iron Deficiency Anemia
In iron deficiency anemia, platelet counts typically remain normal or are mildly to moderately elevated (thrombocytosis), with reactive thrombocytosis occurring in approximately 8-22% of patients, and counts rarely exceeding 1,000 × 10⁹/L, though most thrombocytosis cases range between 450-600 × 10⁹/L.
Typical Platelet Count Range
- The mean platelet count in iron deficiency anemia patients is approximately 310 × 10⁹/L, with most patients maintaining counts within or slightly above the normal range 1
- Thrombocytosis (defined as platelets >450 × 10⁹/L) occurs in 8.1-22% of iron deficiency anemia patients 1, 2
- In patients with iron deficiency anemia and thrombocytosis, the mean platelet count is approximately 522 × 10⁹/L (range typically 450-600 × 10⁹/L) 1
Upper Limits and Extreme Cases
- Platelet counts can occasionally exceed 1,000 × 10⁹/L in severe iron deficiency anemia, though this represents an uncommon extreme 3
- Patients with more severe anemia, lower ferritin levels, and more advanced iron deficiency are more likely to develop higher platelet counts 1
- The degree of thrombocytosis correlates with the severity of iron deficiency, with lower hemoglobin, lower mean corpuscular volume (MCV), lower transferrin saturation, lower serum iron, and higher total iron-binding capacity associated with higher platelet counts 1
Response to Iron Replacement
- Half of patients with thrombocytosis resolve to platelet counts <450 × 10⁹/L within 2 weeks of iron supplementation 1
- All patients with iron deficiency-associated thrombocytosis normalize their platelet counts within 6 weeks of iron replacement therapy 1
- Even patients without baseline thrombocytosis experience a decrease in platelet counts with iron replacement, with median counts dropping from 299 to 265 × 10⁹/L after 3 months of treatment 2
- The platelet count decrease occurs regardless of whether oral or intravenous iron is administered 2
Clinical Pitfalls and Caveats
- Thrombocytopenia (low platelet count) is extremely rare in iron deficiency anemia and should prompt investigation for alternative diagnoses such as immune thrombocytopenia or other concurrent conditions 4, 5
- When thrombocytopenia does occur with iron deficiency anemia, the median platelet count is approximately 30 × 10⁹/L, and this resolves rapidly (median 6 days) with iron replacement 5
- Patients with persistent thrombocytosis despite adequate iron replacement should be evaluated for a concomitant clonal myeloproliferative process 1
- The mechanism of thrombocytosis in iron deficiency anemia is not fully explained by thrombopoietin or other thrombopoietic cytokines, though elevated erythropoietin may play a contributory role 3