Can Iron Deficiency Cause Elevated Platelet Counts?
Yes, iron deficiency anemia commonly causes reactive thrombocytosis, with platelet counts frequently exceeding 450 × 10⁹/L and occasionally surpassing 1,000 × 10⁹/L. 1, 2
Mechanism of Thrombocytosis in Iron Deficiency
- Iron deficiency stimulates megakaryopoiesis (platelet production), with iron saturation being the most important factor affecting platelet counts—as iron saturation decreases, platelet counts increase 2
- The correlation between elevated erythropoietin (EPO) levels and high platelet counts suggests EPO may directly increase platelet production in iron-deficient states 1
- Iron appears to have an inhibitory effect on platelet production, so when tissue iron levels are low, this inhibition is removed, allowing increased platelet counts 2
Prevalence and Clinical Significance
- Thrombocytosis occurs in approximately 28% of women with iron deficiency anemia, while thrombocytopenia is rare (2.3%) 2
- The American Heart Association notes that iron deficiency in cyanotic congenital heart disease patients causes both polycythemia and altered platelet function 3
- Iron deficiency-associated thrombocytosis is not benign—accumulating evidence demonstrates increased thromboembolic risk in both arterial and venous systems 4
Platelet Function Considerations
- Despite elevated platelet counts, platelet function is actually impaired in iron deficiency anemia, with decreased collagen-induced and ADP-induced aggregation 5
- The increased platelet numbers may serve as compensation for decreased platelet function 5
- The American Heart Association describes both decreased platelet number and function abnormalities in certain conditions with iron deficiency 3
Response to Iron Replacement
- Platelet counts normalize with iron replacement therapy, typically decreasing as hemoglobin and iron parameters improve 1, 2
- Rarely, acute thrombocytopenia can occur during iron repletion (platelet counts dropping from 168,000 to 21,000 per mm³ by day 6, or from 725,000 to 105,000 per mm³ by day 10), though this gradually resolves 6
- Iron replacement therapy should be considered an effective preventive strategy against thromboembolic complications in iron-deficient patients with thrombocytosis 4
Clinical Pitfalls to Avoid
- Do not dismiss elevated platelet counts in iron deficiency as "reactive" and therefore harmless—assess thromboembolic risk, particularly in patients with inflammatory bowel disease, chronic kidney disease, or cancer 4
- Monitor platelet counts during iron replacement, as rapid decreases can occasionally occur, though this is uncommon and self-limited 6
- Recognize that the combination of elevated RBC count with decreased mean corpuscular hemoglobin concentration (MCHC) in conditions like polycythemia vera with concurrent iron deficiency requires addressing the underlying myeloproliferative disorder before correcting iron deficiency 7