['Early detection of changes in the glomerular filtration rate (GFR) is crucial in detecting acute kidney injury. There is burgeoning evidence from preclinical and clinical studies that symmetrical dimethylarginine (SDMA) correlates well with different parameters of renal function. In some studies, SDMA even outperformed creatinine as a marker of GFR. It is however unknown how fast SDMA is increasing after reduction in GFR. The aim of our study was therefore to determine the temporal change of SDMA in comparison with cystatin C after a defined reduction in GFR.', 'Blood samples from 24 healthy living-related kidney donors (19 F/5 M), mean age 55.2 ± 8.3 years, were collected prior to donation of the kidney as well as 1, 6, 12, 24, 72 and 168 h after unilateral nephrectomy. SDMA levels were measured using a liquid chromatography-mass spectrometry-based method.', 'Within 6 h after unilateral nephrectomy, i.e. reduction of GFR by 50%, SDMA rose from 0.571 ± 0.120 to 0.659 ± 0.135 µmol/L (P < 0.001). Baseline cystatin C levels increased from 0.87 ± 0.16 to 1.07 ± 0.15 mg/L (P < 0.001). Also, serum creatinine rose significantly within 6 h after removal of one kidney from 65.4 ± 8.4 to 88.8 ± 10.2 µmol/L (P < 0.001).'] Is sDMA an early marker of change in GFR after living-related kidney donation?