BACKGROUND: Diabetic kidney disease is the leading cause of end-stage renal disease worldwide. Whether diabetes mellitus (DM) is an additional factor leading to elevated blood pressure (BP) levels and BP variability (BPV) in patients with chronic kidney disease (CKD) is unknown. This study aimed to compare ambulatory BP levels, BP trends and BPV in diabetic and non-diabetic patients with CKD.METHODS: This study included 48 diabetic and 48 non-diabetic adult patients (>18 years) with CKD (estimated glomerular filtration rate [eGFR] <90 and ≥15 mL/min/1.73 m2), matched in a 1:1 ratio for age, sex and eGFR within each CKD stage (2, 3a, 3b and 4). All patients underwent 24-h ambulatory BP measurement with the Mobil-O-graph device. To evaluate the effect of DM and time on the trajectories of 24-h BP levels, we performed two-way mixed ANOVA analysis for repeated measurements using hourly means. BPV was calculated with validated formulas.RESULTS: In total, patients with DM had significantly higher 24-h systolic BP (SBP; 132.13 ± 10.71 vs. 124.16 ± 11.45; p = 0.001) and pulse pressure (PP; 57.1 ± 9.6 vs. 49.5 ± 10.9; p < 0.001), but similar 24-h diastolic BP (DBP; 75.00 ± 8.43 vs. 74.62 ± 6.86 mm Hg; p = 0.809) compared to patients without DM. A similar trend was evident across all CKD stages. The effect of DM on BP trajectories during the recording period was significant for SBP (F = 18.766, p < 0.001, partial η2 = 0.261) and marginally significant for DBP (F = 3.782, p = 0.057, partial η2 = 0.067). Twenty-four hour SBP SD, weighted SD (wSD) and average real variability (ARV; 10.94 ± 2.75 vs. 9.46 ± 2.10; p = 0.004), as well as 24 h DBP SD, wSD, coefficient of variation (CV) and ARV (8.23 ± 2.10 vs. 7.10 ± 1.33; p = 0.002) were significantly higher in diabetic compared to non-diabetic CKD patients.CONCLUSIONS: Ambulatory SBP and PP levels are higher and SBP-profile is different in patients with diabetic compared to those with non-diabetic CKD. Systolic and diastolic BPV are also higher in diabetics. These findings may signify a higher cardiovascular risk for patients with both DM and CKD compared to patients with CKD alone, through higher BP levels and BPV.