To prevent clotting in the extracorporeal circuit during haemodialysis, anticoagulant treatment is mandatory. In patients without eleveted bleeding risk low-dose unfractionated heparin (UFH) or low molecular weight heparins (LMWHs) can be used. LMWHs is prefered because of proven safety, equal to UFH efficacy, easy handling and other benefits. In ptients with increased bleeding risks, systemic anticoagulation should be avoided. If it is possible, UFH is indicated with whole blood clotting time control. When side effects of heparin therapy during routine haemodialysis occur, the use of UFH has to be avoided or stoped all heparins when heparin-iduced thrombocytopenia type II was suspected