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# Weight - Whole blood and components

## Essential information

Definition/s

  Estimated blood volume (EBV) is calculated using the Nadler formula (see chapter 3.7 of the Guidelines for the Blood Transfusion and Tissue Transplantation Services in the UK).

  Extracorporeal volume (ECV) is the total volume outside the donor’s circulation at any time during a donation procedure. It includes all blood, plasma and components in the collection packs, the machine harness and testing samples.

Obligatory

  Must not donate if:

  1. Under 65 kg (10 stone 3 pounds).
  2. The donor weight means that they have difficulty in getting onto or off the donation couch.
  3. Venous access is very difficult.
  4. The safe weight limit of the bleeding couch/chair is exceeded.
  5. They are a double red cell donor and weigh under 70 kg (11 stone).

  Component donation:

  During any planned component donation procedure, the donor’s ECV must not exceed 16% of their EBV at any point in the procedure.

  Careful consideration should be taken when calculating the EBV for transgender donors to ensure the most appropriate chart is selected.

Discretionary
  1. If male and over 50 kg of weight (7 stone 12 pounds), accept.
  2. If female, 20 years of age or older and over 50 kg of weight (7 stone 12 pounds), accept.
  3. If female, less than 20 years of age with an EBV of 3500 mL or greater (as per Appendix 1), accept.

## Supporting information

See if relevant
  - Appendix 1: EBV for female donors
  - Appendix 3: Maximum permitted ECV for component donors
  - Sleep apnoea
  - Weight loss medication
Additional information

  Limits on donation volume are in place to protect the donor from adverse effects such as fainting.

  There is a minimum legal donor weight of 50 kg at which a donation can be accepted. In young women, there is a significant risk of fainting if their donation exceeds 15% of their EBV thus a minimum EBV of 3500 mL is needed.

  For individuals with a body mass index greater than 40, there is a risk that the formula used to calculate blood volume may result in an overestimation of EBV.

  The 50 kg lower weight limit is not appropriate for double red cell donations because of the increased volume and iron that is being taken from the donor.

Regulatory information

  Part of this entry is a requirement of the Blood Safety and Quality Regulations 2005. Other parts are related to research into the reasons why donors faint.

Reason for change:
  Guidance on the use of weight loss mediation has been moved to a new entry.
Version details:

  WB-DSG Edition 203 Release 78 (28 August 2025)

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