OBJECTIVE To determine equivalence of the mean anti-Xa activity [aXa] in patients with EGFR <60 mL/min treated with a reduced therapeutic dose of nadroparin using the dosage guideline of the Dutch Federation of Nephrology (NfN) and patients with EGFR > 60 mL/min receiving a standard therapeutic dose of nadroparin. DESIGN Prospective, observational, multicentre, cohort study. METHODS In three general teaching hospitals, patients were included between July 20H and April 2016 if they met inclusion criteria: Age > 18 years, therapeutic dose of nadroparin, subcutaneous administration for at least three days and written informed consent. Exclusion criteria were: dialysis, participation in another study and use of anti-Xa inhibitors other than nadroparin or four-factor prothrombin complex concentrate within seven days before the start or during the study. After at least three adjusted doses on the third day of therapy a blood sample was drawn four hours after administration of nadroparin (therapeutic range: 0.6-1.0 lU/mL). RESULTS 97 patients with EGFR <60 mL/min and 100 patients with EGFR > 60 mL/min were included. The mean aXa was 0.63 lU/mL respectively 0.62 lU/mL (P for equivalence = 0.015). In the group with renal impairment 52%, 12% respectively 37% of the patients achieved sub-, supra-And therapeutic aXa, compared with 47%, 7% respectively 46% in the group with normal renal function (P = 0.30). CONCLUSION This study shows that in patients with renal impairment a dosage reduction of therapeutic nadroparin using the dosage guideline of the NfN results in aXa that is equivalent with standard dose treatment in patients with normal renal function.