Living in a prediabetes state significantly increases a patient's risk for both diabetes and cardiovascular disease. Tianqi capsule, containing 10 Chinese herbal medicines, is used in China for the treatment of type 2 diabetes mellitus (T2DM).

The purpose of this study was to assess whether Tianqi prevented T2DM in subjects with impaired glucose tolerance (IGT) over the course of a 12-month treatment.

Individuals with IGT were randomly allocated in a double-blind manner to receive Tianqi (n = 210) or a placebo (n = 210) for 12 months. Oral glucose tolerance tests were conducted every 3 months to assess the development of diabetes or restoration to normal glucose tolerance. All subjects received the same lifestyle education. The primary endpoint was the conversion of IGT to T2DM. Body weight and body mass index were observed. Adverse effects were monitored.

Of the 420 enrolled subjects with IGT, 389 completed the trial (198 in the Tianqi group and 191 in the placebo group). At the end of the 12-month trial, 36 subjects in the Tianqi group (18.18%) and 56 in the placebo group (29.32%) had developed diabetes (P= .01). There was a significant difference in the number of subjects who had normal glucose tolerance at the end of the study between the Tianqi and placebo groups (n = 125, 63.13%, and n = 89, 46.60%, respectively;P= .001). Cox's proportional hazards model analysis showed that Tianqi reduced the risk of diabetes by 32.1% compared with the placebo. No severe adverse events occurred in the trial. There were no statistical differences in body weight and body mass index changes between the Tianqi group and the placebo group during the 12-month trial.

Treatment with a Tianqi capsule for 12 months significantly decreased the incidence of T2DM in subjects with IGT, and this herbal drug was safe to use