blood to individuals with type B or AB.Blood group O  (or blood group zero in some countries) individuals do not have either A or B antigens on the surface of their RBCs, and their blood serum contains IgM anti-A and anti-B antibodies against the A and B blood group antigens. Therefore, a group O individual can receive blood only from a group O individual, but can donate blood to individuals of any ABO blood group (i.e., A, B, O or AB). If a patient in a hospital situation were to need a blood transfusion in an emergency, and if the time taken to process the recipient's blood would cause a detrimental delay, O Negative blood can be issued.  They are known as universal donors.Red blood cell compatibility chartIn addition to donating to the same blood group; type O blood donors can give to A, B and AB; blood donors of types A and B can give to AB.Red blood cell compatibility table[24][25]Recipient[1]Donor[1]O−O+A−A+B−B+AB−AB+O−YNNNNNNNO+Y