These tests may include:
- Fasting blood glucose test: After fasting overnight (at least 8 hours) a blood test can be performed to check your blood sugar. If your blood glucose level is 126 milligrams per deciliter (mg/dL) or above after fasting for 8 hours on two separate testing occasions, you have diabetes. If your blood glucose is between 100 and 125mg/dL, this is considered prediabetes, which is a risk factor for developing type 2 diabetes.
- Random (non-fasting) blood glucose test: If you have a blood sample taken -- regardless of how long it has been since you last ate -- and your non-fasting blood glucose is higher than 200 mg/dL, the doctor will suspect diabetes. This is especially true if you are having other diabetes symptoms such as increased thirst and urination. A fasting blood glucose test must be done to confirm the results.
- Oral glucose tolerance test: This test examines how well your body metabolizes sugar after it is introduced into your body. After fasting overnight, the doctor will provide you with a sample of sugary liquid to drink. Then, a blood sample is taken every 30 to 60 minutes after you drink the solution for 2 to 3 hours. Diabetes is diagnosed if your blood glucose level is higher than 200 mg/dL after 2 hours. If your blood glucose is between 140 and 200 mg/dL it is considered “impaired glucose tolerance” or prediabetes.
Your doctor may do other tests to distinguish between type 1 and type 2 diabetes, which is an important consideration in determining how best to treat the condition. A test for your blood insulin level can help determine that you have type 1 diabetes if it shows that you have little or no ability to produce insulin. Another test is a blood test for immune system molecules called antibodies directed against the beta cells of the pancreas, which are found only in people with type 1 diabetes.
Your doctor may also recommend a glycated hemoglobin (A1C) test, which shows your average blood sugar level over the past two to three months. It works by measuring the percentage of blood sugar attached to hemoglobin, the oxygen-carrying protein in red blood cells. The higher your blood sugar levels, the more hemoglobin you’ll have with sugar attached. Generally, a target A1C result is 7 percent or less.