OBJECTIVETo observe the effect of Danzhi Jiangtang capsule (DJC) on the clinical indexes and vascular endothelial function indexes in patients with impaired glucose tolerance (IGT).METHODSA total of 106 patients were enrolled and randomly assigned to the treatment group and control group following a four-week washout period. The patients in the control group received a general lifestyle intervention, while those in the treatment group received DJC (2.0 g 3× a day) in conjunction with the intervention given to the control group patients. The physiological and biochemical levels, vascular endothelial function indices, and traditional Chinese medicine (TCM) syndrome ratings of the patients in the two groups were compared after 12 weeks of therapy.RESULTSIn the control group, the diastolic blood pressure (DBP) was significantly improved compared with those before treatment (83.31 ± 6.47 vs. 79.21 ± 6.17, p < .01) (CI: 1.45, 6.73; Cohen's d: 10.51), as was the case with the nitric oxide (NO) levels and TCM syndrome points (35.71 ± 4.58 vs. 43.96 ± 5.17, 9.57 ± 2.63 vs. 5.38 ± 1.79, p < .001) (CI: -10.28, -6.24; 3.12, 5.18; Cohen's d: 0.90). In the treatment group, the levels of fasting blood glucose, endothelin and vascular endothelial growth factor were significantly improved compared with control group (4.92 ± 0.21 vs. 5.59 ± 0.31, 59.37 ± 13.25 vs. 72.13 ± 12.37, 19.25 ± 2.80 vs. 26.76 ± 1.88, p < .001) (CI: 0.55, 0.78; 7.40, 18.13; 6.52, 8.50; Cohen's d: 4.94, 0.41, 1.32), as was the case with 2-h post-load plasma glucose and total cholesterol (TC) (8.33 ± 0.62 vs. 8.89 ± 1.55, 4.61 ± 1.05 vs. 5.22 ± 1.12, p < .05) (CI: 0.07, 1.07; 0.15, 1.06; Cohen's d: 0.40, 0.51).CONCLUSIONSTreatment with DJC could significantly improve the physiological and biochemical indicators, vascular endothelial function, and TCM syndrome points of IGT patients, indicating that DJC could be a potential drug to treat patients with IGT of Qi-Yin deficiency type.