Tests Used to Diagnose Type 2 Diabetes

Type 2 diabetes is a serious medical condition that involves high blood sugar levels. It occurs when the body cannot process glucose (sugar) properly. About one-third of adults in the United States with diabetes don't know they have the disease. If you have symptoms or are at risk for diabetes, talk to your healthcare provider about getting tested.

Learn about type 2 diabetes, its signs and symptoms, the tests used to diagnose the condition, and more.

Doctor testing patient blood sugar for diabetes in examination room
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Signs and Symptoms of Type 2 Diabetes

Many people with type 2 diabetes don't know they have it. Some people may not have symptoms, while others' symptoms are too mild to recognize. However, there are some warning signs to take note of.

Symptoms of type 2 diabetes may include:

While recognizing symptoms is important, it's also helpful to be aware of risk factors for type 2 diabetes. These include:

Additionally, African American, American Indian, Asian American, Hispanic/Latino, and Pacific Islander populations, and people over the age of 35, have a higher prevalence of a type 2 diabetes diagnosis.

Tests Used to Diagnose Type 2 Diabetes

There are multiple tests that could be used to check for type 2 diabetes. The specific test used depends on the individual, their symptoms, and risk factors.

Fasting Blood Sugar Test

The fasting blood sugar test is a blood test used to check the glucose levels in your blood after eight to 10 hours of fasting (other than water). A needle is placed into a vein to pull out a small amount of blood for testing. This test is usually scheduled in the morning after fasting all night and before any food is eaten.

Fasting Blood Sugar Test Results

  • Normal: Lower than 100 milligrams of glucose per deciliter of blood (mg/dL)
  • Prediabetes: 100–125 mg/dL
  • Diabetes: Higher than 125 mg/dL

Hemoglobin A1C Test

The hemoglobin A1C test is also known as the A1C or HbA1c test. It's a blood test that checks average blood sugar levels over the past two to three months by measuring the amount of glucose found on hemoglobin A protein in the blood. Once the glucose sticks to the protein, it remains for the entirety of the protein's lifespan (up to 120 days), providing a two to three month average even though blood is only drawn once. This test does not require fasting.

Hemoglobin A1C Test Results

  • Normal: Lower than 5.7% (average blood sugar)
  • Prediabetes: 5.7%–6.4%
  • Diabetes Higher than 6.4%

Random Blood Sugar Test

The random blood sugar test is also known as the random or casual plasma glucose test. It is typically used when someone is experiencing severe diabetes symptoms and is taken any time of the day regardless of whether they have recently eaten. This test does not differentiate between the normal range and the prediabetes range.

Instead, a result of 200 mg/dL or more is considered diabetic. If the results are below the level that indicates diabetes, your healthcare provider may suggest another test to screen for prediabetes.

Random Blood Sugar Test Results

  • Normal and Prediabetes: Lower than 200 mg/dL
  • Diabetes: 200 mg/dL or higher

Oral Glucose Tolerance Test

The oral glucose tolerance test is a blood test that involves checking blood glucose levels at two different times. Blood is drawn for the first time after a person has gone without food or beverages other than water for at least eight hours.

Blood is drawn and tested again two to three hours after drinking a specific, sugary drink. The process allows medical professionals to see how the body responds to sugar. This test is often used to check for gestational diabetes in pregnant women.

Fasting Blood Sugar Test Results

  • Normal: Lower than 140 mg/dL
  • Prediabetes: 140–199 mg/dL
  • Diabetes: 200 mg/dL or higher

Who Should Be Tested

Early testing for diabetes is important since the disease is reversible. Lifestyle changes, such as eating a healthy diet and incorporating regular exercise to lose weight, can help. Many people with type 2 diabetes don't know they have it, so if you're experiencing diabetes symptoms or are at risk, it's a good idea to get tested for diabetes.

Reasons to be tested for type 2 diabetes include:

  • Having overweight or obesity
  • Low physical activity levels
  • Diet high in sugars or processed foods
  • History of gestational diabetes or having a baby more than 9 pounds at birth
  • Polycystic ovary syndrome (PCOS) diagnosis
  • Thick, dark skin near the neck or armpits called acanthosis nigricans
  • Heart, brain, or leg blood vessel disease
  • Impaired fasting glucose, impaired glucose tolerance, or prediabetes diagnosis
  • Blood pressure reading of 140/90 millimeters of mercury (mm/Hg) or higher
  • High-density lipoprotein (HDL) cholesterol (considered "good" cholesterol) lower than 35 mg/dL or a triglyceride (another fat in the blood) level 250 mg/dL or higher
  • Family members with diabetes
  • Over age 45
  • Identify as a race or ethnicity with a higher prevalence of diabetes diagnoses (African American, Hispanic/Latino American, American Indian and Alaska Native, Asian American, or Pacific Islander populations)

Next Steps

After being tested for diabetes, the following steps depend on the test results and other factors specific to the individual, such as their symptoms and lifestyle.

Test results may show blood sugar levels in one of the following ranges:

Some individuals may be asked to take additional blood tests.

If your blood sugar levels are higher than normal but lower than those considered diabetic, you are in the prediabetic range. Prediabetes means you are at an increased risk of developing diabetes.

Lifestyle changes, such as increasing physical activity and eating more nutritiously, can reverse a prediabetes and type 2 diabetes diagnosis. If your blood sugar levels are in the diabetic range, your healthcare provider may discuss medication in addition to lifestyle changes.


Type 2 diabetes is a serious medical condition that involves high blood sugar due to the inability to process glucose properly. Testing blood sugar levels can determine if you have prediabetes or type 2 diabetes. Anyone who is at an increased risk of diabetes, or experiencing symptoms, should be tested.

Several blood sugar tests may be used, including the fasting blood sugar test, the hemoglobin A1C test, the random blood sugar test, and the oral glucose tolerance test. Your healthcare provider will determine which test is best for you.

If results determine prediabetes or type 2 diabetes, your healthcare provider will discuss the next steps with you. These may include additional testing, lifestyle changes such as nutrition and exercise, and medications.

A Word From Verywell

Suspecting, being diagnosed with, and living with type 2 diabetes can be challenging. If you or someone you know is at high risk of diabetes or is experiencing symptoms, reach out to a healthcare provider to see about testing. Prediabetes and type 2 diabetes can be managed and reversed with lifestyle changes, but getting tested is the first step toward treatment and recovery.

Frequently Asked Questions

  • Can you test for type 2 diabetes at home?

    Yes, it is possible to test blood sugar levels at home. However, these tests cannot be used to diagnose diabetes. Anyone who has symptoms or risk factors for diabetes should see a medical professional for testing.

  • How often should you test your blood sugar?

    People taking insulin to manage their diabetes may test their blood sugar multiple times daily. For a diabetes diagnosis, how often you get tested depends on your risk level. Some people may test every three years, while others may test multiple times per year. Check with a healthcare provider to determine when to get tested.

  • Can you have diabetes without knowing it?

    Yes, it is possible to have diabetes without knowing it. Some people may not have symptoms, while others are too minor to recognize. About one-third of adults with type 2 diabetes do not know they have diabetes.

14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Ashley Olivine, Ph.D., MPH
Dr. Ashley Olivine is a health psychologist and public health professional with over a decade of experience serving clients in the clinical setting and private practice. She has also researched a wide variety psychology and public health topics such as the management of health risk factors, chronic illness, maternal and child wellbeing, and child development.