Although there is widespread use of herbal dietary supplements that are believed to benefit type 2 diabetes mellitus, few have been proven to do so in properly designed randomized trials; their efficacy for intermediate-term glucose control remains unclear. Pancreas Tonic is a botanical mixture of traditional Indian Ayurvedic herbs currently available as a dietary supplement. We report the results of a single-center, randomized, double-blind, placebo-controlled 3-month trial of Pancreas Tonic in type 2 diabetic patients inadequately treated with diet/lifestyle or stable doses of sulfonylureas and/or metformin for at least 3 months. Patients with type 2 diabetes for >/= 1 year were entered into 2 strata of hemoglobin A(1c) (HbA(1c)) levels (stratum 1: 8.0% to 9.9%; stratum 2: 10.0% to 12.0%). All subjects began a 1-month single-blind placebo run-in phase, followed by randomization in a 2:1 ratio of active treatment: placebo, to 3 months of double-blind treatment with either Pancreas Tonic or matching placebo (2 capsules 3 times a day). Concurrent oral agents were continued unchanged throughout the study. The primary outcome was the change in HbA(1c) from randomization; results of each stratum were analyzed independently. The baseline characteristics of 36 subjects who completed the study were comparable between treatment groups. Nineteen subjects entered stratum 1 and 17 entered stratum 2. A statistically significant reduction of HbA(1c) from randomization to end-of-study was seen in the stratum 2 subjects (Pancreas Tonic: 10.1% +/- 1.0% to 8.8% +/- 1.9%, P =.004; placebo: 10.8% +/- 1.4% to 11.2% +/- 1.8%, not significant [NS]). No significant HbA(1c) reductions were seen in the stratum 1 subjects. There were no significant treatment-related differences in the fasting plasma glucose (FPG), lipids, body mass index (BMI), body composition, blood pressure, insulin sensitivity estimates using the minimal model, glucose and insulin responses to a meal challenge, quality of life, adverse events, or other safety indices between treatment groups. Pancreas Tonic was well tolerated. Treatment with Pancreas Tonic (2 capsules 3 times per day) for 3 months significantly improved glucose control in type 2 diabetic patients with HbA(1c) levels between 10.0% to 12.0%. This study represents the first properly designed, prospective intervention trial of therapy with an Ayurvedic herbal supplement for intermediate-term glucose control in type 2 diabetes.