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Diabetes Testing and Diagnoses

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What are examples of tests for diabetes and how is it diagnosed?

  • Diabetes is diagnosed with blood tests
  • The simplest is called a fasting blood sugar or FBS
    • Two FBS tests are taken during two different occasions to make the diagnosis of type 2 diabetes
  • The oral glucose tolerance test or OGTT is also a blood test
    • It takes a little more time (two hours), but only one test is usually required to confirm a diagnosis
  • A1C blood tests are taken to track the changes on blood sugar over the previous 3 months
    • The A1C is less effective in some racial groups than in Non-Hispanic Whites
    • For example, the A1C is less reliable among Phillipino and several Asian racial groups
      • For the American Indian or Alaska Native who has mixed blood parentage, the A1C also may be less reliable in you

What is a fasting blood sugar (FBS) test?

  • This means that a sample of the blood is drawn usually in the morning–after not eating or drinking (except water) for 8-12 hours.
  • The concentration of glucose or sugar in the blood is examined
  • FBS results:
    • Normal =less than 99 mg/dl
    • Pre diabetes=100-125 mg/dl
    • Diabetes=126 mg/dl or higher
  • Two FBS tests taken over two different time periods are required to confirm a diagnosis of Type 2 diabetes

What is mg/dl?

  • mg/dl means "milligram per deciliter"
  • It is used to measure blood sugar (glucose) concentration
  • This measurement may also be written as mg%.

What is oral glucose tolerance test (OGTT)?

  • An OGTT is usually a 2-hour oral glucose tolerance test
  • The person has a fasting blood sugar (FBS) test
  • Then they are then given a concentrated sugar drink
  • Exactly 2 hours after the sugar drink, another blood test sample is drawn to check the level / concentration of sugar (glucose) present in the blood
  • This test is only needed once but requires that you remain close to the clinic for two hours
OGTT results
  • OGTT measures fasting blood sugar before and after a person drinks a solution containing concentrated glucose (sugar),.
  • OGTT results mean pre-diabetes if:
    • FBS is 100-126 mg/dl or less.
    • And the second test is 140-199 mg/dl two hours after the glucose drink.
  • OGTT results mean diabetes is 200+ mg/dl after 2 hours

What is an A1C test (also called hemoglobin A1C (HbA1C), glycated hemoglobin, or glycohemoglobin test)?

  • Hemoglobin is in the red blood cells (carries oxygen to every cell in the body)
  • Sugar in the blood attaches to hemoglobin and creates hemoglobin A1C
  • The more sugar in the blood, the higher percentage of cells with hemoglobin A1C
  • Red blood cells live for about 3 months
    • The sugar you have eaten over the past three months is attached to those cells
    • So, an A1C test is a blood test that reflects your average blood glucose levels over the past 3 months