No, O+ red cells cannot be given to B− patients. The ABO/Rh rules block it, and the crossmatch would reject the unit anyway. ## Why not B− patients’s plasma carries antibodies that would attack O+ red cells. A mismatched unit clumps inside the patient, the exact danger compatibility rules exist to prevent. ## What B− patients CAN receive B− patients can receive red cells from: O−, B−. ## What O+ donors can do instead Your red cells still help: O+, A+, B+, AB+, that is real, needed work. Register and let a compatible patient near you find you when the call comes. Plasma rules also run opposite to red cells (explained here).
Compatibility
Can O+ donate blood to B−?
No, O+ red cells cannot go to B− patients. Which groups B− can receive from, and what O+ donors can do instead.
People also ask
Can O+ donate blood to B−?
No, B− patients can only receive from O−, B−.
Is O+ to B− safe in emergencies?
No, emergencies make compatibility matter more, not less; unknown-group patients get O−.
Where is this decided?
The blood bank crossmatch (see the crossmatch guide), never self-matched at home.
About this article
Written by Assam Blood Donor team. Medical review: pending, content follows published national (NBTC/NACO) guidance and is for general education, not personal medical advice. Last updated 11 Sept 2026.
Sources: NBTC donor selection criteria · standard donation-centre practice
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Reading is step one. Registering is step two.
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