Weight

Acceptability at Recruitment

QUALIFIED

Acceptability at VT / Work-Up

QUALIFIED

Individual at Risk

Donor

Explanation of Condition

To calculate body mass index (BMI), use this calculator: https://www.nhs.uk/health-assessment-tools/calculate-your-body-mass-index/

Justification

BMI is the most reliable tool to assess the body composition within the scientific community, and it is the criteria to based our decision upon, however it is an imperfect assessment. BMI may not be always accurate, particularly in ethnic minority groups. It is recognised that a high BMI does not always reflect body habitus and some high BMI donors may be fit and suitable to donate.

It should be strictly followed at recruitment but donors outside these limits at work-up should be discus with the medical officer who may allow them to proceed after discussion with the Medical Director.

Guidance

AT RECRUITMENT

Acceptable

• For PBSC - if BMI less than, or equal to, 40.0.

• For BMH - if BMI less than, or equal to, 35.0.

AT VT

Acceptable

• For PBSC - If BMI less than, or equal to, 40.0 (If BMI 40-43 discuss with MO).

• For BMH - If BMI less than, or equal to, 35.0 (If BMI 35-40 OR discuss with MO).

Donors with a borderline BMI can be considered on a case-by-case basis please see additional guidance below.

For donors >18 years of age, please refer to the following link for the chart on what is acceptable/ not acceptable: https://www.med-guidelines.org.uk/images/c/cc/Weight_categories_for_16-17_year_olds.png

Please discuss with a MO if the donor is showing to be outside the healthy range.

Underweight

Adult donors weighing less than 30 kg should not be accepted, since the volume of the cell separator machine’s extracorporeal circuit would then exceed 15% of the donor’s total blood volume, with unacceptable risks of hypovolaemia and/or vasovagal issues.

Discuss with MO any donor with weight <45kg or <50kg if donor's weight is significantly less than the recipient with a MO (consider CC discussion if concern over blood volume).

Donors with a low BMI should be assessed for any underlying eating disorder or medical condition contributing to their weight. It is also important to ensure they are not experiencing symptoms related to a low BMI.

For donors with a low weight, check with the TC to confirm whether the weight discrepancy is acceptable.

Overweight or obese

Potential donors with higher BMIs may have higher risk of complications prior, during and after the procedure

• PBSC (BMI >40-43) - Risk is less clear than BM so greater discretion may be used. Poor venous access and need of central line insertion (and its subsequent complications) is more likely. Other considerations include ability to mobilise on to or off donation couch. Donors who are overweight or obese tend to have more moderate to severe pain with PBSC donation.

• BMH (BMI >35-40) - Bone marrow harvest is a more difficult procedure in overweight donors. They should be carefully assessed for additional anaesthetic risk factors (e.g. cardiovascular, respiratory and endocrine disease). If no additional risk factors donor may at discretion of MO proceed to medical assessment when an anaesthetic opinion is mandatory and donor examined to decide whether it is technically possible. The collection centre must be alerted to this additional requirement before donor is sent to medical.

Pseudonyms or Related Conditions

Obesity

Overweight

Underweight

Version

Version 1, Edition 6

Date of Last Update

25th June 2026 29th October 2026