Tang-min-ling pills are made by Chinese herbs extract, and data showed they had antidiabetic effects on the experimental rats and no obvious toxicity was found.This is a randomized, doubled blind, dose-paralleled-control multi-centre clinical trial to evaluate the efficacy and safety of Tang-min-ling pills in the treatment of type 2 diabetic patients and explore the optimal dosage of Tang-min-ling pills.

Two hundred and ten of overweight patients inflicted with primary diabetes mellitus who had stagnated heat of liver and stomach syndrome were recruited, which were randomly divided into 3 groups, and were given high-dosage (12g Tang-min-ling pills every time), low-dosage (6g Tang-min-ling pills every time)、placebo by 3 times every day for 12 weeks respectively. Hemoglobin A1c (HbA1c), Fasting plasma glucose (FPG)、postprandial 2 hours plasma glucose(2hPG)、syndrome、symptoms、body mass index (BMI)、waist circumference (WC) of these groups were measured and analyzed. Some safety indexes such blood and urine and stool routine examination, electrocardiogram (ECG)and liver and kidney function tests were measured and analyzed during the experiment. The treatment period is 12 week.

Inclusion Criteria:

1. Patients with primary type 2 diabetes mellitus
2. BMI ≥ 24 kg•m-2
3. 30-70 years old
4. HbA1c≥7.0%, and FPG>7.0 mmol/L, but <13.9 mmol/L or 2hPG>11.1 mmol/L
5. Informed consent has been signed
6. stagnated heat of liver and stomach syndrome according to TCM syndrome differentiation

Exclusion Criteria:

1. The patients accepted diabetic treatment for more than a month continuously
2. The patients were treated by drugs in 3 week before they were given test drugs
3. Diabetic ketosis, diabetic ketoacidosis or serious inflammation in a month
4. The contractive pressure >160 mmHg or diastolic pressure >100 mmHg
5. Pregnant, preparing for pregnancy or breast-feeding women
6. Mental patients
7. The patients who have serious heart, lung, liver, kidney and brain or other primary complications
8. Allergic persons
9. The patients who are attending other clinical trial
10. The patients who have serious diabetic complications
11. The patients who ever attended this clinical trial
12. Alcohol and / or psychoactive substances, drug abuse and dependency
13. The person maybe loss for some reason such as work or life condition according to the investigator's judgement
14. The lipid-lowering or antihypertensive drug dosage and category which the patients are taking couldn't be kept stable
15. The patients who are eating some drugs or health food which can affect the body weight