Background: Serum creatinine measured by point-of-care testing (CrP) correlates with central laboratory serum creatinine (CrC) measurement and can be performed frequently, which might lead to an earlier diagnosis of acute kidney injury (AKI). We aimed to test whether the combination of CrP and CrC measurement would achieve earlier and more freuent AKI diagnosis than routine CrC testing alone. Methods: Retrospective study of critically ill patients with two or more CrP measurements 24 h before an AKI was diagnosed on CrC. Results: 1591 patients with a median APACHE 3 score of 67 (IQR 52-85) and a median number of CrP of 5 (IQR 3-6) measurements. The median individual differences in time to AKI diagnosis between CrC and CrP was −5 h (−11-−1). As the number of point-of-care tests increased in the 24 h before CrC-defined AKI diagnosis, the difference in hours increased (−3 (IQR −6-−1) to −8 (IQR −13– −2); p < 0.001). Compared to CrC alone, the use of both CrC and CrP detected more increases in AKI severity to each AKI stage (stage 1: 1767 (34 %) vs 1.170 (30 %); stage 2: 1.301 (25 %) vs 809 (21 %) and stage 3: 2071 (40 %) vs 1920 (49 %); p < 0.001). Conclusion: Combined with CrC, CrP measurement resulted in the earlier diagnosis of AKI during ICU admission. Compared to CrC alone, using CrP measurements in combination with CrC was also associated with a higher maximum AKI stage and more detection of worsening AKI.