The search for new anticoagulants requires simple and affordable methods for primary determination of their activity. Clotting tests are widely used for laboratory evaluation of the hemostatic system. These are model studies that assess the state of the hemostatic system from a clinical point of view based on the fibrin clot formation time. Reagents and instruments for such tests are produced in Russia, they have low manufacturing cost and are easy to use. However, it is necessary to make a few modifications to the measurement methods to assess the anticoagulant activity. The study was aimed to demonstrate performance of the protocol for testing the solution anticoagulant activity using the modified standard clinical tests involving measurement of the activated partial thromboplastin time (aPTT), prothrombin time (PT), and thrombin time (TT). Reagents for measurement of aPTT, PT, and TT were used, along with the domestically produced heparin and two recombinant anticoagulant proteins from the medicinal leech obtained in our laboratory. Clotting tests were performed with the addition of anticoagulants to the reaction mixture were performed; performance and applicability limits of the methods used were determined. When studying hirudin, heparin, and cysteine-rich anticoagulant of medical leech using measurement of aPTT, TT, and PT, a dose-dependent increase in clotting time was demonstrated. The methods’ compatibility with the use of various common components of buffer solutions used in biochemical tests was determined. It was shown that the slightly modified standard blood clotting tests for determination of hemostatic parameters could be used to test new potential anticoagulants.