Blood Draw Guidance

Whenever the volume of blood to be removed in 24hr will exceed 1% of whole blood volume (WBV) of the participant, hematocrit should be determined in advance, to ascertain that it is not <38%. The frequency of monitoring hematocrit levels should be commensurate with the volume of blood to be removed, and the estimated vulnerability of the subject to blood loss.

Calculate the average blood volume for a small individual who might participate in your study to determine whether your study is likely to exceed the 1% threshold, and thus should plan on measuring hematocrit. The table below represents an average of the WBV range based on participant age, which can be used as a heuristic.

Particular illnesses, conditions, and treatments are associated with a low blood Hb level, blood volume depletion, and/or reduction of the body’s ability to replenish the blood taken through sampling. Consider reducing the volume of blood to be removed from populations with the following (or similar) conditions:

• Renal failure
• Bone marrow dysfunction
• Chemotherapy
• Cardiovascular, pulmonary or hematopoietic problems

The following blood draw guidelines are generally deemed to pose no more than minimal risk to research participants (see References) but do not replace clinical judgement. Thus, lesser blood draw volumes than those stated herein may be prudent. Protection of human participants is the first priority.  If the study protocol necessitates greater blood draw volumes, IRBMED may consider approving the project only if the added risk can be justified by the expected direct benefit to the participant.

Lower blood draw volumes for children who are already sick or hospitalized are prudent even when the illness, injury and/or treatment is not likely to affect blood volume or oxygen carrying capacity.

Any study that draws more than 50mL total over 8 weeks from a child participant requires review at an IRB convened meeting.

NOTE: The administration of blood transfusions does not alter the suggested maximum volume to be drawn.

Blood draws for healthy adults should be limited to 10.5mL/kg subject body weight or 550 mL, whichever is less, over an 8-week period.

NOTE: The administration of blood transfusions does not alter the suggested maximum volume to be drawn.

1. Gammon RR, ed. Standards for blood banks and transfusion services. 32nd ed. Bethesda, MD: AABB, 2020. https://www.aabb.org/standards-accreditation/standards

   Reference Standard 5.4.1A. Whole Blood Volume Collected. Maximum of 10.5 mL/kg of donor weight, including samples.

2. Howie SR. Blood sample volumes in child health research: review of safe limits. Bull World Health Organ. 2011;89(1):46-53. PMC3040020

   A literature review cataloguing a range of paediatric blood sample volume limits that are consistent with physiological “minimal risk.”

3. Nadler SB, Hidalgo JH, Bloch T. Prediction of blood volume in normal human adults. Surgery. 1962; 51(2):224–32. [PubMed: 21936146]. Qtd in Liu 2019:

   There are several methods available for [whole] blood volume [(WBV)] calculations. One of the most popular methods uses the Nadler equations:

   Men: BV = 0.3669 × h³ + 0.03219 × w + 0.6041

   Women: BV = 0.3561 × h³ + 0.03308 × w + 0.1833

   Where h=body height in meters, w=body weight in kilograms, BV=Blood volume in liters.

4. Peplow C et al. Blood draws up to 3% of blood volume in clinical trials are safe in children. Acta Paediatr. 2019 May; 108(5): 940–944. PMC6587985

   “We conclude that protocols that schedule regular blood draws of up to 2.4 mL/kg body weight corresponding to 3% of total blood volume at each visit are not associated with a risk of anaemia or other clinically relevant side effects in young children. Our data were generated in children who had no disease‐associated increased risk of anaemia. The risk of anaemia and adverse events may increase for sick children, especially those associated with low blood haemoglobin levels or blood volume depletion and when treatment may induce anaemia.”

5. Raes et al. A reference frame for blood volume in children and adolescents. BMC Pediatr. 2006; 6: 3. PMC1434736

   Blood volume is calculated most accurately based on Lean Body Mass, but calculations are also shown based on other height, mass, and BMI. For adolescents, but not for infants and younger children, “we have to take into account sex and pubertal stage differences.”