Blood Draw Guidance

Jan 3, 2022 10:00 pm

Blood draws for research purposes should be limited to the smallest necessary volume.

Maximum blood draw volumes for research should also take into account blood drawn for clinical care.  Investigators should coordinate with clinical teams regarding total blood draw volumes for a given patient.  In determining blood draw volumes, the participant’s potential benefit should be considered. Priority should be given to:

  1. Samples required for clinical care
  2. Samples for research with potential for direct benefit
  3. Samples for research with indirect benefit only
  • Considerations

    Measuring hematocrit

    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.

    Source: Kleinman K, Mcdaniel L, Molloy M. Harriet Lane Handbook. Access through ClinicalKey (level-1 login required).
    Age average WBV (mL/kg)
    Preterm infants 100
    Term newborns 80
    1 - 12 months 75
    1 - 3 years 75
    4 - 6 years 80
    7 - 18 years 85
    Adults 70


    Conditions affecting blood volume and/or hematocrit

    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
  • Suggested Maximum Volume Drawn

    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.

    Body mass (kg) Sick or hospitalized - mL within 24hr Healthy - mL within 24hr Healthy - mL within 8wk
    3 7.2 12 24
    4 9.6 16 32
    5 12 20 40
    6 14.4 24 48
    7 16.8 28 56
    8 19.2 32 64
    9 21.6 36 72
    10 24 40 80
    11-15 26.4 - 36 44 - 60 88 - 120
    16-20 38.4 - 48 64 - 80 128 - 160
    21-25 50.4 - 60 84 - 100 168 - 200
    26-30 62.4 - 72 104 - 120 208 - 240
    31-35 74.4 - 84 124 - 140 248 - 280
    36-40 86.4 - 96 144 - 160 288 - 320
    41-45 98.4 - 108 164 - 180 328 - 360
    46-50 110.4 - 120 184 - 200 368 - 400
    >50 120 200 10.5 mL/kg or maximum 550mL



    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.

  • References

    Additional sources on WBV and safe blood draw limits:

    1. Gammon RR, ed. Standards for blood banks and transfusion services. 32nd ed. Bethesda, MD: AABB, 2020.

      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 Paediatr2019 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.”


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Last Updated: January 3, 2022 10:00 PM