What tests should be done for diabetes?
Early detection of diabetes helps maintain blood sugar levels and prevent organ damage. Here are the ten best tests for diagnosing diabetes.

Diabetes (diabetes mellitus) is a disorder in which your blood glucose levels are consistently elevated. If left untreated, high blood sugar damages various organs, such as the eyes, nerves, kidneys, and others, potentially leading to death.

Diabetes testing has become more important because evidence suggests that early treatment with suitable drugs can help maintain healthy blood glucose levels and prevent early organ damage. This lowers the rate of premature death.

There are several varieties of diabetes. Irrespective of the presence or absence of signs of diabetes, several tests are conducted to assess your risk of acquiring particular kinds of diabetes or obtaining a diabetes diagnosis.

10 tests to diagnose diabetes

  1. Fasting plasma glucose (FPG) test
    • The FPG blood test detects the amount of glucose in your blood at a specific time. It is advisable to undergo this test in the morning after you have fasted for at least eight hours for the most accurate results. Fasting entails not eating or drinking anything but sips of water.
      • The normal value: Less than 100 mg/dL.
      • Prediabetes: 100 to 125 mg/dL.
      • Diabetes: 126 mg/dL or higher.
  2. Hemoglobin A1c (HbA1c)
    • Hemoglobin A1c test, also called glycated hemoglobin test and glycohemoglobin, analyzes average glucose levels over three months. This basic blood test identifies how much glucose is linked to red blood cells.
      • The normal value: 4 to 6 percent.
      • Prediabetes: 5.7 to 6.4 percent.
      • Diabetes: 6.5 percent and higher.
  3. Random plasma glucose (RPG)
    • This test is done at any time in the day without the need for fasting. This test is usually done if the doctor detects the presence of diabetes symptoms.
    • A result of 200 mg/dL or above on a random glucose test suggests that you may have diabetes. However, the doctor will normally repeat the test on a different day to ensure a more accurate diagnosis.
    • It is beneficial for patients who require a quick diagnosis, such as those with type I diabetes, or immediate supplemental insulin.
  4. Post prandial glucose test (PPBS)
    • Glucose levels in the blood are tested in this test, particularly after a meal. Normally, blood glucose levels rise after a meal, which causes the pancreas to release insulin. In people with diabetes, insulin may not be produced or utilized properly, so the blood glucose levels remain high.
    • PPBS test is done to measure blood glucose levels precisely two hours after consuming a meal. Glucose levels in healthy people have normally decreased by this stage, but they may still be elevated in people with diabetes. As a result, it functions as a test to determine whether you have diabetes or are effectively regulating your blood glucose levels.
      • The normal value: 120 to 140 mg/dL.
      • Prediabetes: 140 to 160 mg/dL.
      • Diabetes: 200 mg/dL and higher.
  5. Oral glucose tolerant test (OGTT)
    • It takes two hours to complete the oral glucose tolerance test. First, a blood sample is drawn to test for glucose after fasting for eight hours. You will be given a sweet drink containing 75 grams of glucose and another test is done two hours later. This test allows your doctor to assess how your body handles glucose.
      • The normal value: 140 mg/dL or below.
      • Prediabetes: 140 to 199 mg/dL.
      • Diabetes: 200 mg/dL and higher.
    • This test is usually used to test gestational diabetes.
  6. Glucose challenge test
    • This is another version of OGTT, where a fasting test is not done. Blood sugar levels are measured after one to two hours after consuming the glucose drink. This test is usually done in pregnant women between 24 and 28 weeks of gestation or at any time during pregnancy if they are at a high risk of developing gestational diabetes.
      • The normal value: 140mg/dL or below.
      • Prediabetes: 140 to 199 mg/dL.
      • Diabetes: 200 mg/dL and higher.
  7. Serum fructosamine levels
    • This test is often used in pregnant women as an alternative to HbA1c. The HbA1c in gestational diabetes may be erroneous. The level of fructosamine in the blood reflects the glucose levels over the previous two to three weeks.
  8. Autoantibodies test
    • Autoantibodies against pancreatic cells can be detected in the blood of people with type I diabetes. The presence of these autoantibodies confirms the diagnosis of type I diabetes.
      • GAD65 or GAD65H, called GAD or pancreatic islet cell autoantibodies
      • ICA512, called islet cell autoantibodies (ICA)
      • Islet antigen 2, called IA-2 or tyrosine phosphatase-related islet antigen
      • Insulin autoantibody (IAA), ZNT8A
  9. Genetic testing
    • The presence of specific variations of the HLA-DQA1, HLA-DQB1 and HLA-DRB1 genes indicates an increased chance of acquiring type I diabetes. This gene family is responsible for identifying the proteins produced by the body and proteins obtained from outside sources. Type I and II diabetes can be determined by this test.
  10. C-peptide test
    • C-peptide is a chemical produced by the pancreas along with insulin. The levels of C-peptide will indicate the levels of insulin produced in the body. Lower levels of C-peptide indicate low levels of insulin. Type I and II diabetes can be determined by this test.
    • Testing for changes in other blood parameters and organs will help determine the presence of diabetes.

SLIDESHOW

Diabetes: What Raises and Lowers Your Blood Sugar Level? See Slideshow

4 types of diabetes

  1. Prediabetes
    • Prediabetes is a condition where blood glucose levels are higher than normal but not high enough to be called diabetes.
    • Prediabetes occurs when your body does not produce enough insulin or is incapable of utilizing it to maintain normal glucose levels in the body. Persistent higher-than-normal levels of glucose can damage your organs in the long run.
    • Prediabetes can develop into type I or type II diabetes. All people with type II diabetes usually transition from prediabetes. Early detection of prediabetes and timely treatment may delay the onset of type II diabetes.
  2. Type I diabetes
    • Type I diabetes is usually seen among children and young adults. This is a chronic condition where blood glucose levels are constantly high due to a lack of insulin hormone in the body. This is an autoimmune condition where the immune cells destroy the pancreatic cells, so the pancreas loses the ability to produce insulin.
  3. Type II diabetes
    • Type II diabetes is a condition usually seen among people older than 45 years. However, younger people can have type II diabetes.
    • Type II diabetes is a condition where the body cannot use the insulin produced leading to high blood glucose levels in the body. Diet changes and regular medication can help maintain normal blood glucose levels.
  4. Gestational diabetes
    • Gestational diabetes is high blood sugar (glucose) levels in the blood during pregnancy. This condition usually goes away after the baby is born and blood glucose levels return to normal. It can occur at any time of pregnancy although it is most frequent during the second or third trimester.
    • It occurs when your body is unable to generate enough insulin, a hormone that helps manage blood sugar levels to fulfill your increased requirements during pregnancy.
    • Gestational diabetes can create complications for both you and your baby throughout pregnancy and after delivery. However, if the illness is diagnosed early and adequately handled, the risks can be reduced.

Things to know about diabetes

  • The number of cases of diabetes is increasing worldwide.
  • According to the statistics released by the Diabetes Research and Clinical Practice in 2019, about 463 million people worldwide suffer from diabetes.
  • The Centers for Disease Control and Prevention estimated that 37.3 million people in the United States have diabetes.
  • Diabetes has a genetic predisposition and runs in the family.

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Medically Reviewed on 4/21/2022
References
Image Source: iStock image

Patel P, Macerollo A. Diabetes mellitus: diagnosis and screening. Am Fam Physician. 2010 Apr 1;81(7):863-70. https://www.aafp.org/afp/2010/0401/p863.html

American Heart Association. Symptoms, Diagnosis and Monitoring of Diabetes. https://www.heart.org/en/health-topics/diabetes/symptoms-diagnosis--monitoring-of-diabetes

American Diabetes Association. Understanding A1C: Diagnosis. https://www.diabeteuttjs.org/diabetes/a1c/diagnosis