Type 2 diabetes diagnosis

If your healthcare provider believes that you may have diabetes, he or she will likely conduct a series of tests¹⁵ that measure your blood sugar levels.

One common form of testing for diabetes is called a glycated hemoglobin test (or A1C test). This blood test is used to measure the percentage of blood sugar attached to your hemoglobin (the oxygen-carrying protein in red blood cells) and, indicate your average blood sugar level over the past 2–3 months.

The more glucose is attached to your hemoglobin, the higher your blood sugar levels. An A1C level below 5.7% is considered normal. An A1C between 5.7–6.4% indicates prediabetes, while an A1C of 6.5% or higher on two separate tests indicates diabetes.

In some cases, the results from A1C tests alone cannot be used to diagnose diabetes. The results may be inconsistent, you may have certain conditions that can make the A1C test inaccurate (such as if you are pregnant¹⁶, as A1C levels can be falsely low in the 2nd trimester, but may rise in the 3rd trimester), or the test may be unavailable.

If A1C tests are not sufficient to diagnose diabetes, the following tests may be used:

• Random blood sugar test: In this test, a blood sample is taken at a random time, regardless of when you last ate. A random blood sugar level of 200 milligrams per deciliter (mg/dL)—or 11.1 millimoles per liter (mmol/L)—or higher suggests diabetes.
• Fasting blood sugar test: A blood sample is taken after fasting overnight (not eating or drinking anything but water for at least 8 hours). A fasting blood sugar level less than 100 mg/dL (5.6 mmol/L) is considered normal. A fasting blood sugar level from 100–125 mg/dL (5.6–6.9 mmol/L) is considered prediabetes, while 126 mg/dL (7 mmol/L) or higher on two separate tests indicates diabetes.
• Oral glucose tolerance test: This test can be used as a screening tool to help diagnose type 2 diabetes, but is most commonly used in diagnosing diabetes in pregnancy (gestational diabetes). A blood sample is taken after fasting for at least 8 hours or overnight. The patient is then given a sugary solution to drink and blood sugar levels are generally drawn 1–3 hours later, as directed by your prescriber. In general, a blood sugar level from 140–199 mg/dL (7.8–11.0 mmol/L) is considered prediabetes.

You should see your healthcare provider if you suspect yourself or your child of having diabetes. By determining the right diagnosis, your provider can administer the proper treatment for your condition.