Blood glucose levels can be ascertained through tests like fasting plasma glucose (FPG) that is done when fasting more than 8 hours. FPG less than 110 mg/dL is considered as normal; a fasting blood sugar ranges between 100 to 125 mg/dL is considered as prediabetes or borderline to develop diabetes, and an FPG range above 126 mg/dL is typically considered as diabetic.

An additional test is called postprandial plasma glucose (PPG). This test should be done 2 hours after a meal and if the results show blood glucose of more than 200 mg/dL then it may be considered a case of diabetes.

In some cases, the doctor may deploy a sensor of Continuous Glucose Monitoring System (CGMS) for 6-14 days. The CGMS is modern technology for diabetes monitoring; the CGM works through a tiny sensor inserted under our skin, usually on the belly or arm.

The sensor measures our interstitial glucose level, which is the glucose found in the fluid between the cells.

The sensor records the blood glucose level at an interval of 5 minutes and records 288 blood glucose reading per day. After 6-14 days the sensor is removed and basis the report, the doctor prescribes either lifestyle modifications or medications.

The amount of glucose in the bloodstream is regulated by the hormone insulin that is secreted in small amounts by the pancreas. When the amount of glucose in the blood rises to a certain level, the pancreas release more insulin that pushes more glucose into the cells. This causes the glucose levels in the blood to drop.

Insulin also helps to store glucose in fat cells (Adipose tissue) and liver (for later use when we are not eating) and it increases the usage of glucose from the peripheral muscles.

Diabetes is caused if our body cannot produce sufficient insulin or if it cannot utilize insulin properly (Insulin resistance).