Blood Donation: Age and Weight Restrictions
Updated May 2026
Reference summary
Age and weight thresholds for blood donation are set to protect donors from adverse reactions (vasovagal events, iron depletion, fluid imbalance) and to ensure adequate collection volume. The current thresholds in the US and UK are documented below; final eligibility is decided at the donation visit by the donor health check. This page summarises published criteria and is not medical advice.
The US thresholds
The American Red Cross sets the minimum age at 17 (16 with parental consent in many states; the specific state-level rules vary). There is no upper age limit; donors in their seventies, eighties, and even older can donate if they meet the health criteria at each visit. The Red Cross has reported on regular donors over 100 in good standing.
Minimum weight is 110 lb (50 kg). Haemoglobin minimum is 12.5 g/dL for women and 13.0 g/dL for men, checked by finger-prick at each visit. There is no specific upper weight limit, but the donor health check at each visit determines fitness to donate.
For Power Red (double red cell apheresis), the additional thresholds are minimum 5'1" height and 130 lb weight for women, and 5'3" height and 150 lb weight for men, with corresponding higher haemoglobin requirements. The procedure removes more red cell mass per visit, so a larger total blood volume is needed to keep the proportion safe.
The UK thresholds
NHS Blood and Transplant sets the minimum age at 17. The previous upper limit for new donors of 65 was removed in 2018. Existing donors can continue past 70 with annual confirmation of good health from their GP. The change followed evidence from the EN-RBC and other studies that healthy older donors do not have higher complication rates than younger donors.
Minimum weight is 7 stone 12 lb (50 kg) and the maximum is 25 stone (158 kg). Haemoglobin minimum is 125 g/L for women and 135 g/L for men. The maximum weight reflects practical donor-chair and equipment fit limitations rather than safety concerns at the donation itself.
The UK does not have a Power Red equivalent in routine practice. Apheresis platelet donation is widely available and requires similar weight thresholds to the US (minimum 50 kg for both sexes for platelet apheresis). Plasma apheresis was paused in the UK after the vCJD pandemic and reintroduced in 2021 for limited use.
Why 50 kg minimum weight
The standard whole blood donation collects about 470 mL (slightly less than a US pint, slightly more than a UK pint). Total blood volume in adults is approximately 70 mL per kg of body weight, so a 50 kg donor has about 3,500 mL total blood volume. The 470 mL donation is about 13.4 percent of total volume in a 50 kg donor, and a smaller percentage in heavier donors.
The threshold of 50 kg keeps the donation at a safe percentage of total blood volume. Below 50 kg, the proportion rises and the risk of vasovagal reactions (light-headedness, fainting) increases substantially. The threshold is also pragmatic: it can be confirmed by a single weight measurement without complex calculations.
The UK JPAC Transfusion Guidelines and the AABB technical manual both reference the 50 kg threshold and the underlying volume-percentage rationale.
The teen donor question
Teen donors (16-19) are an important segment of the US blood supply, supported by high-school blood drives. They also have higher rates of vasovagal reactions and iron-deficiency anaemia than older donors, especially repeat teen donors. The Red Cross has additional safeguards including extended post-donation observation and lower donation frequency limits for teen donors.
UK teen donors must be 17 or older, and the high-school drive model is less common than in the US. Many UK universities run campus drives that recruit students at the start of higher education.
For both jurisdictions, paediatric donation (under 16) is not part of the regular adult-supply system. Specialised paediatric programmes exist for autologous donation (donating for one's own future surgery) and for directed family donations.
Older donor changes
The 2018 UK removal of the upper age limit for new donors was driven by demographic projection (more older adults available, fewer younger adults of donor age) and by safety data showing healthy older donors are no more likely to have adverse events than younger donors. The condition is annual GP confirmation of good health for donors continuing past 70.
The US has never had an upper age limit. Donors are evaluated individually at each visit. The Red Cross has actively recruited from the older-adult demographic as the supply pressures of the late 2010s and early 2020s have intensified.
The practical considerations for older donors are the same as for any donor: adequate haemoglobin, blood pressure within range, no active illness, no recent qualifying medications. Iron repletion may take longer in older donors, so donation frequency may be reduced from the maximum allowed.
Haemoglobin: the gating step at each visit
Even if you meet age and weight criteria, you can be deferred at the visit for low haemoglobin. The threshold of 12.5 g/dL (US, women) or 125 g/L (UK, women) reflects the lowest level at which donation is safe without putting the donor into iron deficiency. Donation removes about 200 mg of iron per unit, which takes 8 to 12 weeks (or longer in some donors) to replenish.
Persistent low haemoglobin should prompt iron repletion (dietary plus oral supplement) and, if it does not resolve, investigation by your GP for underlying causes (gastrointestinal blood loss, menstrual blood loss, malabsorption). Frequent donors and women in their reproductive years are at higher risk of donation-related iron depletion than other donors.
The Red Cross runs an Iron-Replacement Programme that mails iron supplements to frequent donors. NHSBT provides iron supplementation guidance on its donor portal. Many regular donors take a daily ferrous sulfate or ferrous gluconate supplement during periods of frequent donation.