This is a single-center, open-label, prospective study. Blood glucose was measured at different time points during oral glucose tolerance testing in patients with type 2 diabetes mellitus, using both venous plasma and multi-channel microspatial offset Raman scattering spectroscopy (mμSORS). Venous plasma glucose was set as gold standard.The two measurements were collected synchronously so as to calculate the mean absolute relative difference (MARD) and the consensus error grid (CEG). Accuracy of non-invasive blood glucose testing by mμSORS will be validated. MARD for two measurement methods in different blood glucose ranges and the safety outcomes of mμSORS such as adverse events will also be assessed.

In order to clinically verify the accuracy and safety of non-invasive blood glucose measurement by the mμSORS technology, and to explore the feasibility of non-invasive detection in multi-indicators of mμSORS, this study will conduct an oral glucose tolerance test on patients with type 2 diabetes. There will be 12 collection points of blood samples as follows: 0-min and post glucose-load 15-min，30-min，45-min，60-min，75-min，90-min，105-min，120-min，135-min，150-min， and 180-min. Approximately 4ml of whole blood was collected at each time point for venous plasma glucose and serum insulin measurement. The blood glucose value measured by mμSORS will be obtained synchronously at the above 12 time points.

Inclusion Criteria:

• 1. Subjects with type 2 diabetes mellitus;
• 2. Age ≥ 18 years;
• 3. There are no scars, obvious pigmentation and other factors that interfere with the detection of the palm skin to be tested;
• 4. Fully understand the nature, significance, possible benefits, possible inconveniences or potential risks of this research, and should also understand the research procedures, be willing to complete the entire research process, and provide written consent form.

Exclusion Criteria:

• 1. Type 1 diabetes, monogenic diabetes, pancreatic damage, or secondary diabetes of other causes should be excluded;
• 2. Severe structural heart disease, such as congenital heart disease, rheumatic heart disease, hypertrophic or dilated cardiomyopathy, chronic congestive heart failure (NYHA≥III); acute myocardial infarction within 12 months before enrollment; history of severe liver or kidney dysfunction(MDRD eGFR< 60 ml/min/1.73m2); and mental disorders, etc.;
• 3. With a history of acute complications of diabetes within 3 months before enrollment; or severe chronic complications of diabetes;
• 4. Alcohol dependency or drug abuse;
• 5. Those who have participated in clinical trials of other drugs within 3 months before screening (since the last visit of the previous trial);
• 6. Pregnancy or lactation period;
• 7. Difficulty in venous blood collection or blood-injection-injury phobia;
• 8. Other circumstances that the investigator considers inappropriate to participate in the study.