What is the maximum amount of blood (milliliters, mL) that can be safely removed during phlebotomy?

Maximum Blood Volume for Safe Phlebotomy

The standard volume for therapeutic phlebotomy is 500 mL of blood, which can be safely removed weekly or biweekly in most patients. 1

General Guidelines for Phlebotomy

• Therapeutic phlebotomy typically involves removal of 500 mL of blood per session in adults 1
• For patients undergoing acute normovolemic hemodilution (ANH), the volume that can be safely removed can be calculated using the formula: V = EBV × (Ho − Hf / Hav), where:
  • V = volume to be removed
  • EBV = estimated blood volume (usually 70 mL/kg body weight)
  • Ho = initial hematocrit
  • Hf = desired hematocrit
  • Hav = average hematocrit (mean of Ho and Hf) 1

Safety Considerations

• Hemoglobin/hematocrit should be checked prior to each phlebotomy 1
• Hematocrit should not be allowed to fall by more than 20% of the prior level during phlebotomy 1
• For patients with hemochromatosis, serum ferritin levels should be checked every 10-12 phlebotomies 1
• Normovolemia must be maintained during acute phlebotomy procedures by matching volume replacement with blood removal 1

Special Populations and Considerations

• Patients with cardiac disease require extra caution during phlebotomy:

  • Those with severe myocardial disease (moderate to severe left ventricular impairment, unstable angina, severe aortic stenosis, critical left main stem disease) should undergo phlebotomy with extreme caution 1
  • Patients with cardiac arrhythmias or cardiomyopathy have increased risk of sudden death with rapid mobilization of iron 1

• For athletes, even small blood losses are rapidly replenished, but minimizing blood removal is advised:

  • Each 10 mL of venous blood drawn represents approximately 0.1-0.3% of total blood volume 1
  • For context, light menstrual flow is <36.5 mL, medium flow is 36.5-72.5 mL, and heavy flow is >72.5 mL per cycle 1

Hypovolemic Phlebotomy for Specific Procedures

• In surgical settings such as liver resection, hypovolemic phlebotomy of 7-10 mL/kg of whole blood without volume replacement has been shown to reduce perioperative blood transfusion requirements 2

Risks and Complications

• Common side effects of phlebotomy include vasovagal reactions, hematoma formation, and nerve injury 3
• Excessive phlebotomy can contribute to anemia, particularly in critically ill patients 4, 5
• In intensive care settings, patients are phlebotomized more frequently (mean 3.4 times per day vs. 1.1 times per day in general wards) 4

Monitoring and Follow-up

• For therapeutic phlebotomy in hemochromatosis:

  • Weekly or biweekly phlebotomy is continued until serum ferritin reaches 50-100 μg/L 1
  • Maintenance phlebotomy is then performed at intervals to maintain ferritin between 50-100 μg/L 1
  • Vitamin C supplements should be avoided during phlebotomy treatment 1

• For other procedures requiring phlebotomy, the number of units and total volume removed should be carefully documented in the patient's medical record 1