Human Large-scale metabolomics analysis is facing important challenges to increase its robustness, reproducibility and interoperability. In this context, stable-isotope labeled compounds are increasingly used for identification and quantification of their unlabeled homologs. In this study, two laboratories were involved in an inter-laboratory absolute quantification trial of amino and organic acids in the reference human plasma sample (NIST-SRM-1950) using 24 commercially-available stable-isotope (13C/15N/D) labeled standards, among the 416 identified level-1 metabolites. A pool of the labeled compounds was prepared in concentrations similar to what is expected in human plasma (0.12-67.25 mg/L). The labeled pool, the NIST-SRM-1950 and the spiked NIST-SRM-1950 were analyzed by LC-HRMS using HILIC and C18 chromatography along with QToF instruments in positive and negative modes. Regardless of chromatography or detection mode, above 19 endogenous metabolites and their labeled homologs were detected without any effects on retention times of spiking and matrix. MS-peak areas of endogenous metabolites in spiked NIST-SRM-1950 were not impacted by the isotope addition. Compared to the analysis in buffer, the intensity of the labeled compounds was impacted (attenuation>1 log for half of them) by the dilution in plasma. Calculated absolute concentration of endogenous metabolites were in accordance (±30%) with expected values for 35-58% of metabolites identified with C18 and 18-25% with HILIC. Results obtained for C18 in positive mode were consistent between the two laboratories. HILIC results complemented those from C18 by allowing quantification of metabolites not detected by C18. This preliminary trial demonstrated that isotope-assisted metabolomics could provide comparable and reliable results across laboratories.