Blood is obtained from healthy, non-medicated animals. For defibrinated blood, fibrin removed mechanically during the clotting process without the addition of anticoagulants. Defibrinated horse blood is ideal for blood agar plate preparations.

Blood in Alsever's is used for titration of complement, adsorption procedures, testing for agglutinins/HA assays and for the preparation of stroma as particulate reagents.