Abstract: A cocktail reagent preparation for the rapid production of serum contains thrombin, snake venom, and protamine sulfate. The preparation employs very small quantities of clot promoting substances which behave in a synergistic manner such that rapid clotting of highly heparinized blood is achieved without altering the chemical analysis of the blood enzymes, proteins, sugars, or electrolytes. Thus, clinicians who rely upon the results of such tests can more closely monitor organ and tissue function and adjust patient therapies accordingly.