Contemplated methods and devices for coagulation control allow to establish a more constant dosage of required medication and to quantify/take into account patient-specific sensitivity to warfarin and Vitamin K by using logit (1/INR) as the dependent variable to so stabilize the variance across all values of INR. Moreover, it should be noted that such use simplifies the relation between INR and dose of coumarins or Vitamin K and reduces the number of parameters to be estimated for each patient.