Objective To study the impact of different insulin levels on the conversion from impaired glucose tolerance (IGT) to type 2 diabetes mellitus (T2DM),through analysis of different glycometabolism condition among quinquagenarian population.Methods Subjects enrolled were Beijing habitants who received annual physical examination [ including oral glucose tolerance test (OGTI) ] in the Chinese PLA General Hospital from 2005-2007.According to the OGTT results,the subjects were divided into three groups,including normal glucose tolerance-non-hyperinsulinemia group (NGT-NHIns),IGT-hyperinsulinemia group (IGT-Hins) and IGT-non-hyperinsulinemia group (IGT-NHINS).The prognosis between the year 2009 and 2010 of the three groups was observed.Hyperinsulinemia was diagnosed with fasting serum insulin ≥ 15 mU/L and/or 2-hour serum insulin ≥ 80 mU/L after glucose loading.Results The rate of case number of conversion to T2DM in IGT-NHIns group (42/133) was higher than that in IGT-Hins group (24/154) or NGT-NHIns group (12/126).The HOMA insulin resistance index (HOMAIR) of individuals with IGT-NHIns was lower than that of IGT-Hins [ 0.96 (0.40,3.53 ) vs 2.04 (0.59,23.20),P ＜ 0.05 ],while whole body insulin sensitivity index (WBISI) was higher than that of IGT-Hins [ 7.48 (3.20,31.35 ) vs 3.28 ( 0.86,7.67 ),P ＜ 0.05 ].Modified β-cell function index ( MBCI ) and insulin secretion index (ISI) in IGT-NHIns was poorer than that of IGT-Hins respectively [ 2.57 (0.58,10.98) vs5.17(1.04,65.09); 7.66 (0.99,28.40) vs 17.56 (4.18,96.46),allPvalues ＜0.01].Conclusions The risk of IGT-NHIns progressing into T2DM is higher than that of IGT-Hins. For the prevention of T2DM,individuals with IGT-NHIns should be paid more attention than keeping an eye on IGT-Hins patients.Early control of risk factors could protect β cell function and prevent the progression to T2DM.