The present invention relates to a method for controlling or regulating an apparatus for extracorporeally treating blood in an extracorporeal blood circuit while adding citrate and calcium for the purpose of anticoagulation. The apparatus comprises a dispensing device for dispensing a calcium solution into the extracorporeal blood circuit. The method encompasses outputting a signal to the dispensing device for altering a setting of the dispensing device, in which the setting corresponds to or effects an addition of calcium, a calcium dosage, concentration, amount or rate. The method further encompasses defining or altering the signal with regard to a calcium content or a calcium concentration of a substituate solution used in extracorporeally treating the blood, and detecting the range of values of permissible or allowed settings for the calcium introduced or to be introduced into the extracorporeal blood circuit by the dispensing device, particularly its amount, concentration or dosage.