When should a complete blood count (CBC) be rechecked after a therapeutic phlebotomy?

When to Recheck CBC After Therapeutic Phlebotomy

Check hemoglobin/hematocrit before each phlebotomy session, and recheck CBC every 10-12 phlebotomy procedures (approximately every 3 months) during the induction phase for hemochromatosis. 1

Immediate Pre-Procedure Monitoring

Mandatory hemoglobin/hematocrit measurement is required before every single phlebotomy session. 1 This is non-negotiable for patient safety:

• Postpone the procedure if hemoglobin falls below 12 g/dL 1
• Discontinue phlebotomy entirely if hemoglobin drops below 11 g/dL 1
• This pre-procedure check prevents symptomatic anemia and ensures adequate oxygen-carrying capacity

Interval CBC Monitoring During Treatment

The frequency of comprehensive CBC monitoring depends on the treatment phase:

Induction Phase (Active Iron Removal)

• Order serum ferritin and CBC every 10-12 phlebotomies, which translates to approximately every 3 months 1
• This applies when performing weekly or twice-weekly phlebotomy sessions 1
• Continue this monitoring frequency until ferritin reaches the target of 50-100 μg/L 1

Maintenance Phase (After Achieving Target)

• Monitor ferritin and transferrin saturation every 6 months 1
• CBC frequency can be reduced to align with ferritin monitoring during maintenance 1
• Phlebotomy frequency decreases to 2-6 times per year to maintain ferritin at 50-100 μg/L 1

Context-Specific Monitoring Adjustments

Polycythemia Vera

For patients with PV undergoing therapeutic phlebotomy, the monitoring paradigm differs from hemochromatosis:

• Weekly complete blood counts should be performed from 2 weeks after treatment administration until recovery from cytopenias 2
• If platelet count falls to 30 × 10⁹/L, check counts at least three times per week until recovery occurs 2
• The goal is hematocrit control below 45% without phlebotomy 2

Myeloproliferative Neoplasms (General)

• Full blood count should be checked one month after diagnosis to assess hematologic stability 2
• Then monitor by full blood count and clinical examination every three months 2
• For MP-CMML patients, monthly full blood count for the first three months is recommended to exclude rapid WBC rise 2

Critical Safety Thresholds

Never proceed with phlebotomy without confirming adequate hemoglobin levels. The pre-procedure hemoglobin check is your safety net against iatrogenic anemia. Research demonstrates that therapeutic phlebotomy can be performed safely with appropriate monitoring—one study of 927 phlebotomy procedures in children showed only 33 adverse events, all grade 2 3—but this safety record depends on rigorous adherence to hemoglobin monitoring.

Common Pitfalls to Avoid

• Do not rely solely on ferritin levels to guide phlebotomy frequency—hemoglobin must be checked before each session regardless of ferritin trends 1
• Do not assume patients can tolerate the same phlebotomy schedule throughout treatment—as iron stores deplete, hemoglobin recovery between sessions may slow 4
• Do not forget that ferritin is an acute-phase reactant—inflammation can falsely elevate ferritin levels, potentially leading to over-phlebotomy if you're not monitoring CBC parameters 5

Documentation Requirements

The College of American Pathologists requires specific documentation for therapeutic phlebotomy 6:

• Each phlebotomy must be performed per provider orders, not as voluntary blood donation 6
• Two-way communication between the referring provider and transfusion medicine physician should be documented 6
• Electronic medical records should demonstrate compliance with monitoring requirements 6