We used ¹H nuclear magnetic resonance (NMR) spectroscopy to assess metabolic responses in patients undergoing hemodialysis (HD). We collected 71 samples of plasma and dialysate from 10 patients before, during, and after HD. We used the dialysate as a possible substitute for blood plasma to quantify small metabolites by ¹H NMR. We confirmed TSP (sodium 3-(trimethylsilyl) propionate 2, 2, 3, 3-d4) as a reference of NMR intensity in dialysate. We examined TSP sensitivities in various dialysate spectra and the correlation between signal intensities and added quantities of TSP. We used integrations of signal areas on ¹H NMR spectra of plasma and dialysate to quantify concentrations of creatinine, lactate, alanine, and valine and calculate their ratios between plasma and dialysate. The ratios of metabolites in plasma to dialysate were 3.2±0.4 (creatinine), 3.6±0.5 (valine), 3.8±0.7 (alanine), and 4.0±0.8 (lactate) mM (mean±standard deviation [SD]). The broader distributions of ratios in levels of lactate and alanine suggested their de novo production during the HD session. Estimation of blood metabolite levels using dialysate is useful for quantitative analysis of metabolic status in blood during HD.