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The Diagnostic Tests for Type 2 Diabetes

    The Diagnostic Tests for Type 2 Diabetes

    If you’re experiencing the symptoms of type 2 diabetes or prediabetes (or at risk of developing it) you may want to talk to your doctor about screening tests. Here’s what you need to know about the diagnostic tests for type 2 diabetes and how they are used to diagnose the disease.

    Type 2 Diabetes: All You Need To Know

    Diagnostic Tests for Type 2 Diabetes

    Doctors will likely use more than one screening test to confirm a diagnosis for type 2 diabetes. The available diagnostic tests are:


    HbA1C, also called glycated hemoglobin screening, measures your average blood glucose level for the past 3 months. More specifically, it checks the amount of glucose attached to the hemoglobin, the oxygen-carrying component of the red blood cell. A hemoglobin has a lifespan of roughly 120 days or 3 months.

    What happens during the test?

    You don’t need to prepare anything for the test; there’s also no need for fasting. A healthcare practitioner will draw a blood sample from your arm and then check it for the average blood sugar level.

    How do they diagnose type 2 diabetes using HbA1C?

    The result of glycated hemoglobin screening comes in percentages:

    • An HbA1C of lower than 5.7 percent denotes normal findings.
    • A result of 5.7 percent to 6.4 percent indicates prediabetes.
    • Finally, an HbA1C of 6.5 percent or higher on 2 separate tests means the person has diabetes.

    What else should I know?

    The HbA1C results can be inconsistent. Moreover, it’s not an appropriate test for pregnant women and those who have another form of hemoglobin (variants). Lastly, results could be inaccurate if the person being tested has anemia.

    diagnostic tests for type 2 diabetes

    Fasting Blood Sugar (FBS)

    Many Filipinos are familiar with fasting blood sugar. It’s perhaps the most well-known diagnostic test for type 2 diabetes because it’s straightforward, highly available, and inexpensive. Also called the fasting plasma glucose test, it checks for the blood glucose level at the time of the screening.

    What happens during the test?

    The test is best done in the morning because it requires you to fast for at least 8 hours and not exceeding 14 hours. This means you cannot eat or drink anything (other than sips of water) 8 hours before FBS. In the clinic or hospital, a healthcare worker will draw blood from you and submit it to the laboratory for testing.

    How do they diagnose type 2 diabetes using FBS?

    When you receive the results of your FBS, you’ll see numbers:

    • A blood sugar level of 99 mg/dl or lower is normal.
    • If it’s 100 to 125 mg/dl, it could mean prediabetes.
    • A result of 126 mg/dl or higher on two separate FBS means the patient has diabetes.

    What else should I know?

    In some instances, the doctor may opt for a random plasma glucose test or random blood sugar (RBS), instead of FBS.

    For an RBS, you don’t need to fast; the doctor will draw your blood sample any time of the day, regardless of when you last ate. A result of 200 mg/dl or higher indicates diabetes.

    How To Lower Your Risk of Type 2 Diabetes

    Oral Glucose Tolerance Test (OGTT)

    OGTT, one of the diagnostic tests for type 2 diabetes, is different because it checks how the body is metabolizing glucose. Additionally, the oral glucose tolerance test takes the most time to administer. This is because you need to stay in the clinic or hospital for at least 2 hours to complete the screening.

    What happens during the test?

    For this test, you need to fast for 8 to 12 hours. Hence, like FBS, OGTT is best done in the morning.

    • In the clinic, the healthcare worker will draw your blood and measure your fasting blood sugar level.
    • After that, they will give you a glucose drink (around 75 grams), which tastes like a “very sweet soda.”
    • After drinking the liquid glucose, the healthcare practitioner will periodically measure your blood sugar at 1, 2, or 3-hour mark. This means that they’ll draw a blood sample a few times within 2 to 3 hours.

    How do they diagnose type 2 diabetes using OGTT?

    A fasting blood sugar level of 60 to 100 mg/dl is normal. After the 1-hour mark, a result of less than 200mg/dl is also normal. What the doctors use to diagnose diabetes is the blood sugar level at the 2 hour-mark:

    • A level of less than 140mg/dl is normal.
    • If the result is between 140 and 199 mg/dl, it means that the person has impaired glucose tolerance or prediabetes.
    • Finally, a blood sugar level of 200 mg/dl or more indicates diabetes.

    What else should I know?

    Besides fasting before the test, you also cannot eat anything during the test. If you have medications that you need to take, talk to your doctor about what to do. Many reports say that OGTT detects diabetes with more accuracy than FBS. However, it’s more expensive and requires more time.

    8 Lifestyle Changes to Lower Type 2 Diabetes Risk

    Key Takeaways

    Screening for diabetes is important because it detects the condition early on. This allows you and your doctor to immediately come up with a strategy on how to keep your blood sugar at normal levels.

    There are several diagnostic tests for type 2 diabetes: fasting blood sugar, random blood sugar, HbA1C, and oral glucose tolerance test. Please keep in mind that the values provided above are common measurements. The numbers may change depending on the equipment used or the laboratory where the test is performed.

    Learn more about Type 2 Diabetes here.

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    Hello Health Group does not provide medical advice, diagnosis or treatment.

    Hemoglobin A1C (HbA1c) Test https://medlineplus.gov/lab-tests/hemoglobin-a1c-hba1c-test/#:~:text=A%20hemoglobin%20A1c%20(HbA1c)%20test%20measures%20the%20amount%20of%20blood,the%20rest%20of%20your%20body. Accessed October 8, 2020 A Summary of the Philippines UNITE for Diabetes Clinical Practice Guidelines for the Diagnosis and Management of Diabetes (Part I: Screening and Diagnosis of DM) https://www.asean-endocrinejournal.org/index.php/JAFES/article/view/98/317 Accessed October 8, 2020 Diabetes Tests - Diabetes https://www.cdc.gov/diabetes/basics/getting-tested.html Accessed October 8, 2020 Diabetes https://www.mayoclinic.org/diseases-conditions/diabetes/diagnosis-treatment/drc-20371451 Accessed October 8, 2020 Diabetes Tests & Diagnosis https://www.niddk.nih.gov/health-information/diabetes/overview/tests-diagnosis Accessed October 8, 2020 Diagnosis - Diabetes https://www.diabetes.org/a1c/diagnosis Accessed October 8, 2020 Glucose tolerance test - non-pregnant https://medlineplus.gov/ency/article/003466.htm Accessed October 8, 2020
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    Written by Lorraine Bunag, R.N. Updated Oct 26, 2020
    Fact Checked by Hello Doctor Medical Panel
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