To analyze the clinical significance of the oral glucose tolerance test (OGTT) in the assessment of abnormal glucose metabolism in Chinese patients with hypertension. In this cross-sectional study of 10,173 hypertensive adult patients from eight sites in China, data on patient, clinical and disease characteristics were collected, and fasting plasma glucose (FPG) levels were measured. A subset of 5322 patients also underwent an OGTT. Abnormal glucose metabolism (impaired glucose regulation (IGR) or diabetes mellitus (DM)) was detected in 31.1% of the 10,173 patients by FPG testing and in 67% of the 5322 patients by OGTT. OGTT increased the detection rate by 35.8%. Patients with FPG levels ≥5.6 and ≥6.1 mmol l(-1) had the mean OGTT 2-h plasma glucose levels of 8.79 and 9.68 mmol l(-1), respectively. Compared with normoglycemic patients, those with IGR or DM had higher rates of total proteinuria (normoglycemic 15.8% vs. IGR 22.1% vs. DM 33.7%, P<0.001), a lower absolute estimated glomerular filtration rate (eGFR; in ml min(-1) per 1.73 m(2)) (82.9 vs. 80.77 vs. 79.74, P=0.06) and a higher prevalence of cardiovascular disease (normoglycemic 17.6% vs. IGR/DM 13.8%, P<0.001). Abnormal abdominal circumference, eGFR ≤60 ml min(-1) per 1.73 m(2), and proteinuria were independently associated with abnormal glucose metabolism (IGR or DM). Hypertensive patients who are diabetic or at risk of diabetes are at greater risk of renal damage and cardiovascular disease than those who are normoglycemic. It is insufficient to assess the glucose metabolism status of Chinese hypertensive patients using only FPG testing; the use of OGTT can increase the detection rate by 35.8%. Patients whose FPG levels were <5.6 mmol l(-1) may be found to have abnormal glucose metabolism after an OGTT.