How do I confirm if I have diabetes?

Blood tests are the main form of diabetes and pre-diabetes diagnosis. Testing enables healthcare providers to find and treat diabetes, or pre-diabetes, which in turn can delay or prevent the development of type 2 diabetes.

The following tests can be used for diagnosis:

1. Hemoglobin A1c, HbA1c, or glycohemoglobin test
2. Fasting plasma glucose (FPG) test
3. Oral glucose tolerance test (OGTT)

A practitioner may ask for multiple tests to confirm a clinical diagnosis. Some tests may be asked to be repeated a second time.

The HbA1C test is a blood test that reflects the average blood glucose levels over the past 3 months, but not its daily fluctuations. This test is used to detect type 2 and pre-diabetes. It is not recommended for diagnosis of type 2 or gestational diabetes.

HbA1C results are reported as a percentage; the higher the percentage, the higher the blood glucose levels.

A normal HbA1C level is below 5.7 percent.

An HbA1C of 5.7 to 6.4 percent indicates prediabetes. People diagnosed with prediabetes may be retested in 1 year. People with an HbA1C below 5.7 percent may still be at risk for diabetes, depending on the presence of other characteristics that put them at risk, also known as risk factors.

People with an HbA1C above 6.0 percent should be considered at very high risk of developing diabetes. A level of 6.5 percent or above means a person has diabetes.

HbA1C does not require fasting, is diagnostically stable/sound, and does not display value instability during stress or illness.

There are several factors that may interfere with use of HbA1C test for diagnostics.
1. Age. The HbA1C test is restricted to adults. The parameters/levels of this test have been optimized for adults, never identified for children or adolescents.
2. Race. The HbA1C levels may vary with race.
3. Anemia or hemoglobinopathy. Abnormal hemoglobin may interfere with the readings of HbA1C levels. This should be taken into consideration.

The FPG test is used to detect diabetes and pre-diabetes and has been the most common test used for diagnosing diabetes. The FPG test measures fasting blood glucose (fasting for at least 8 hours).

People with a fasting glucose level of ≥ 5.6-6.9mmol/l (100-125 mg/dL) have impaired fasting glucose (IFG), or prediabetes. A level of ≥ 7 (126 mg/dL) or above, confirmed by repeating the test on another day, means a person has diabetes.

This test is used to diagnose T1D onset in the presence of elevated glucose levels.

The OGTT can be used to diagnose diabetes, prediabetes, and gestational diabetes. Research has shown that the OGTT is more sensitive than the FPG test, but it is less convenient to administer. When used to test for diabetes or prediabetes, the OGTT measures blood glucose after a person fasts for at least 8 hours and 2 hours after the person drinks a liquid containing 75 grams of glucose dissolved in water.
If the 2-hour blood glucose level is between 140 and 199 mg/dL, the person has a type of prediabetes called impaired glucose tolerance (IGT). If confirmed by a second test, a 2-hour glucose level of 200 mg/dL or above means a person has diabetes.

Both type 1 and type 2 diabetes can go undiagnosed, due to the general symptoms which may be mistaken for other illnesses. Blood glucose levels must be tested if two or more symptoms are present.

Diagnosis of Gestational Diabetes (GDM)

Women with elevated blood glucose levels and present two or more symptoms undergo screening by OGTT. This usually occurs during early pregnancy or between 24 to 28 weeks of pregnancy.