Blood Type Guide

ABO and Rh Blood Groups

Blood type is determined by antigens on red blood cells. ABO system: Type A: A antigens on cells, anti-B antibodies in plasma. Type B: B antigens, anti-A antibodies. Type AB: both antigens, no antibodies — universal recipient for red cells. Type O: no antigens, both anti-A and anti-B — universal donor of red cells (in emergency). Rh factor: positive (+): Rh antigen present. Negative (−): no Rh antigen. Rh-negative individuals can develop anti-Rh antibodies if exposed to Rh-positive blood. Receiv

Compatibility Rules

Red blood cells compatibility rule: the donor's ABO type must not have antigens that the recipient has antibodies against. O negative is the universal donor for red cells (no antigens to cause reaction). AB positive is the universal recipient (no antibodies to react). Plasma compatibility: REVERSED from red cells. Plasma contains antibodies. Type AB plasma: no antibodies (can donate to anyone — universal plasma donor). Type O plasma: contains both anti-A and anti-B (can only give to type O). Pla

UK Blood Type Distribution

UK blood type prevalence: O positive: 35%. A positive: 30%. B positive: 8%. AB positive: 3%. O negative: 13%. A negative: 8%. B negative: 2%. AB negative: 1%. O negative (universal donor) is relatively rare at 13% of the population but is the most in-demand blood type for emergency use. NHS Blood and Transplant always needs O negative donors. AB positive is the rarest in terms of population but most flexible as a recipient. Ethnic variations: South Asian populations have higher rates of B positi

Blood Donation in the UK

NHS Blood and Transplant accepts donations from: age 17+ (first donation up to age 66). Weight 7 stone 12 lbs (50kg) minimum. Most people can donate every 12 weeks (red cells). Whole blood donation takes approximately 10-15 minutes. Total appointment 45-60 minutes including health checks. Criteria that may defer: recent tattoo or piercing (4 months). Travel to certain countries (malaria risk — up to 12 months). Certain medications. Frequency: maximum 3 times per year for women, 4 for men (iron l

Not medical advice. This calculator is for general information and education only. Figures are estimates and may not reflect your circumstances. For decisions, consult your GP or a qualified healthcare professional. See our editorial standards.

Blood Type Compatibility — Transfusion & Donation

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