Maximum Acceptable Hemoglobin and RBC Levels for Blood Donation
Blood donors are typically accepted with hemoglobin levels up to 18 g/dL for men and 16.5 g/dL for women, though donors with persistently elevated hemoglobin above these thresholds require clinical evaluation to exclude polycythemia vera and other pathological causes before donation eligibility can be determined.
Standard Upper Hemoglobin Limits
The WHO criteria for polycythemia vera define upper limits as 18.5 g/dL (11.5 mmol/L) for men and 16.5 g/dL (10.2 mmol/L) for women, above which donors should be evaluated for underlying pathology 1.
Blood donors found to have hemoglobin ≥18 g/dL represent approximately 1.58% of the donor population and are predominantly male 2.
Most blood donation services do not routinely screen for upper hemoglobin limits, focusing instead on minimum thresholds, though donors with visibly elevated hemoglobin warrant further investigation 3.
Clinical Evaluation of High Hemoglobin Donors
When donors present with persistently elevated hemoglobin above polycythemia thresholds, the following evaluation is recommended:
JAK2 V617F and JAK2 exon 12 mutation testing should be performed in donors with concurrently high hemoglobin, high hematocrit, and iron deficiency to screen for polycythemia vera 1.
Complete blood count including RBC, platelet count, and white blood cell count should be obtained, as polycythemia vera typically shows elevations across multiple cell lines 1.
Erythropoietin levels, ferritin, mean cell volume, and routine clinical measurements help distinguish primary from secondary causes 1.
Secondary Causes of Elevated Hemoglobin
Approximately 61% of donors with high hemoglobin have identifiable secondary causes of erythrocytosis rather than primary polycythemia 2:
Smoking and occupational exposure to carbon monoxide are the most common attributable factors (70.4% of high hemoglobin donors) 2.
Severe hypertension, including renal artery stenosis, accounts for additional cases 1.
Diabetes mellitus and other chronic conditions may contribute 1.
Risk of Polycythemia Vera in Blood Donors
Among donors with hemoglobin ≥18 g/dL who underwent JAK2 mutation testing, none tested positive for polycythemia vera in one study of 24 donors 2.
In a separate study of 46 donors with repeated hemoglobin above WHO polycythemia limits, only 2 (4.3%) had confirmed polycythemia vera 1.
High hemoglobin in blood donors is therefore less likely due to polycythemia vera and more commonly represents secondary erythrocytosis 2.
Management Recommendations
Donors with hemoglobin above polycythemia thresholds should be counseled to stop or reduce smoking to decrease thrombosis risk, regardless of donation eligibility 1.
Donors with confirmed secondary causes and no evidence of polycythemia vera may be reconsidered for donation after appropriate clinical evaluation 2.
Approximately 10-22% of donors with persistently elevated hemoglobin should be permanently deferred based on identification of polycythemia vera or other serious underlying conditions 1.
Among donors with initially elevated hemoglobin who donated again within 6 months, hemoglobin levels were significantly lower on repeat testing, suggesting transient elevations are common 1.
Important Caveats
Capillary hemoglobin measurements may underestimate venous hemoglobin by 0.67-1.07 g/dL, meaning some donors with apparently high capillary readings may have acceptable venous levels 4.
The difference between capillary and venous hemoglobin is greater in winter (0.78-1.26 g/dL) compared to summer (0.56-0.88 g/dL), suggesting seasonal variation 4.
Deferring donors solely based on high hemoglobin without clinical evaluation may unnecessarily exclude healthy donors and increase donor anxiety 2.