Although direct oral anticoagulants do not need laboratory testing for dose adjustment, there are instances when laboratory measurement of the drug anticoagulant effect may be useful. They include before initiation of treatment, before surgical or invasive procedures, on the occasion of hemorrhagic or thrombotic events, and whenever immediate reversal of anticoagulation is needed. Choice of tests should be primarily based on their prompt availability. Accordingly, the dilute-thrombin or the ecarin clotting times are best suited for dabigatran and the prothrombin time or the anti-FXa for rivaroxaban.