Blood transfusion of transfusing uncrossmatched blood, O-negative blood is used, followed by crossmatch as soon as possible. O-negative is also used for children and women of childbearing age. It is preferable for the laboratory to obtain a pre-transfusion sample in these cases so a type and screen can be performed to determine the actual blood group of the patient and to check for alloantibodies. This chart shows possible matches in blood transfusion between donor and receiver using ABO and Rh system. In the same way that the safety of pharmaceutical products is overseen by pharmacovigilance, the safety of blood and blood products
Jehovah's Witnesses and blood transfusions decide whether they could conscientiously accept fractions used from blood for purposes such as vaccination. This position has been expanded on since; the pre-formatted Durable Power of Attorney form provided by the Watch Tower Society includes an option for Jehovah's Witnesses to "accept all fractions derived from any primary component of blood." In 1964, Jehovah's Witnesses were prohibited from obtaining transfusions for pets, from using fertilizer containing blood, and were even advised (if their conscience troubled them) to write to dog food manufacturers to verify that their products were blood-free. Later that year, it was stated that doctors or nurses