Blood donors should be healthy adults, receiving appropriate medications for prevention of parasites such as heartworm or other vector-borne diseases. Donors should not have been previously transfused, or in some species, not sensitized by prior pregnancy. Canine donors should be typed for DEA 1, and those that are positive should be used only for positive recipients. Those that are negative are used for all negative recipients and any recipient that cannot be typed. Some dogs with immune-mediated hemolytic anemia cannot be typed because they have autoagglutination, which cannot be cleared by washing RBCs. In some situations, typing reagents may not be available, or severe blood loss may require transfusion before typing results are available.
Feline donors should be typed, and type A donors should be readily available. It is helpful if a type B donor has been identified and can be called in if type B blood is needed. A compatible major and minor crossmatch can replace typing in cats if necessary.
Canine donors should be heartworm negative, and depending on local disease prevalence be tested for Ehrlichia canis, Anaplasma phagocytophilum, Aplatys, Babesia canis, B gibsoni, and Mycoplasma. Greyhounds are commonly used as donors because they normally have a higher hematocrit than most other dogs, but they are at higher risk for B canis infection, so they should be tested. For the same reason, Pit Bulls should be tested for B gibsoni.
Feline donors should be tested negative for Mycoplasma and retroviruses. Both canine and feline donors should have normal hematocrits. Generally, a maximum donation should not exceed 20 mL/kg. Horses and cattle should be tested negative for retroviruses.