The genes identified so far in people with type 2 include many that affect the insulin-producing beta cells of the pancreas, says Craig Hanis, PhD, a professor at the Human Genetics Center at the University of Texas Health Science Center in Houston. And yet he emphasizes that why people get type 2 isn't at all clear yet: "What it tells us is that diabetes is a complicated disease."

Several tests are helpful in identifying DM. These include tests of fasting plasma glucose levels, casual (randomly assessed) glucose levels, or glycosylated hemoglobin levels. Diabetes is currently established if patients have classic diabetic symptoms and if on two occasions fasting glucose levels exceed 126 mg/dL (> 7 mmol/L), random glucose levels exceed 200 mg/dL (11.1 mmol/L), or a 2-hr oral glucose tolerance test is 200 mg/dL or more. A hemoglobin A1c test that is more than two standard deviations above normal (6.5% or greater) is also diagnostic of the disease.
Regular ophthalmological examinations are recommended for early detection of diabetic retinopathy. The patient is educated about diabetes, its possible complications and their management, and the importance of adherence to the prescribed therapy. The patient is taught the importance of maintaining normal blood pressure levels (120/80 mm Hg or lower). Control of even mild-to-moderate hypertension results in fewer diabetic complications, esp. nephropathy, cerebrovascular disease, and cardiovascular disease. Limiting alcohol intake to approximately one drink daily and avoiding tobacco are also important for self-management. Emotional support and a realistic assessment of the patient's condition are offered; this assessment should stress that, with proper treatment, the patient can have a near-normal lifestyle and life expectancy. Long-term goals for a patient with diabetes should include achieving and maintaining optimal metabolic outcomes to prevent complications; modifying diet and lifestyle to prevent and treat obesity, dyslipidemia, cardiovascular disease, hypertension, and nephropathy; improving physical activity; and allowing for the patient’s nutritional and psychosocial needs and preferences. Assistance is offered to help the patient develop positive coping strategies. It is estimated that 23 million Americans will be diabetic by the year 2030. The increasing prevalence of obesity coincides with the increasing incidence of diabetes; approx. 45% of those diagnosed receive optimal care according to established guidelines. According to the CDC, the NIH, and the ADA, about 40% of Americans between ages 40 and 74 have prediabetes, putting them at increased risk for type 2 diabetes and cardiovascular disease. Lifestyle changes with a focus on decreasing obesity can prevent or delay the onset of diabetes in 58% of this population. The patient and family should be referred to local and national support and information groups and may require psychological counseling.
Doctors can also measure the level of a protein, hemoglobin A1C (also called glycosylated or glycolated hemoglobin), in the blood. Hemoglobin is the red, oxygen-carrying substance in red blood cells. When blood is exposed to high blood glucose levels over a period of time, glucose attaches to the hemoglobin and forms glycosylated hemoglobin. The hemoglobin A1C level (reported as the percentage of hemoglobin that is A1C) reflects long-term trends in blood glucose levels rather than rapid changes.
According to the Mayo Clinic, doctors may use other tests to diagnose diabetes. For example, they may conduct a fasting blood glucose test, which is a blood glucose test done after a night of fasting. While a fasting blood sugar level of less than 100 milligrams per deciliter (mg/dL) is normal, one that is between 100 to 125 mg/dL signals prediabetes, and a reading that reaches 126 mg/dL on two separate occasions means you have diabetes.