A Review of The A1c Test

November is National Diabetes Month. In honor of this very important month I would like to review the Hemoglobin A1c test (also referred to as A1c).

What is the A1c test?

• The A1c test is a measure of your average blood glucose over the past 2 to 3 months.
• The A1c test measures how much glucose attaches to the hemoglobin portion of red blood cells.
• The higher the blood glucose is, the more glucose that will attach to hemoglobin, thus increasing A1c.
  • Hemoglobin is a protein in the red blood cell responsible for carrying oxygen body tissues.
  • Red blood cells are constantly forming and dying. The average lifespan of a red blood cell is 3 months.

Why is the A1c test done?

• The A1c test can be done to diagnose diabetes and is also used to assess diabetes control for those with established diabetes.
• The Diabetes Control and Complications Trials (DCCT) was a landmark study that showed that tight glycemic control, as measured by A1c, could reduce the risk of microvascular complications (such as retinopathy and nephropathy).

When is the test done?

• The test can be done at any time of day and does not require fasting

How often should I have it done?

• The 2015 Standards of Medical Care In Diabetes recommends:
  • “Perform the A1C test at least two times a year in patients who are meeting treatment goals (and who have stable glycemic control)."
  • “Perform the A1C test quarterly in patients whose therapy has changed or who are not meeting glycemic goals”

What are the target A1c ranges?

• Normal: 4 to 5.6 %
• Pre-diabetes: 5.7 to 6.4 %
• Diabetes Diagnosis: >6.5 % (* Repeat testing should be done in the absence of absolute hyperglycemia)

A1c goal if you have diabetes:

 
The 2015 Standards of Medical Care In Diabetes recommends:

• <7 % (for non-pregnant adults)
• A lower goal, 6.5 %, may be recommended for those with short duration of type 2 diabetes, long life expectancy, treatment is either lifestyle changes or Metformin and there is no significant history of cardiovascular disease

How do I calculate my average blood glucose from my A1c test?

Estimated average glucose (eAG) is calculated as follows:

• eAG= (A1c x 28.7) – 46.7
• Example:
  • A1c: 8 %
  • eAG: 183
    • (8 x 28.7) – 46.7

What conditions may cause a falsely high or falsely low A1c test result?

• False LOW A1c
  • Hemolysis (premature breakdown of red blood cells)
  • Certain hemoglobinpathies (inherited group of blood disorders)
  • Chronic liver disease
  • Chronic kidney disease
  • Recent blood transfusion
  • High triglycerides
  • Certain medications (make sure to keep your physician up to date on all your current medications)
• False HIGH A1c
  • Iron deficiency
  • Vitamin B 12 deficiency
  • Alcoholism
  • Uremia (buildup of urea and other waste products in blood)
  • Hyperbilirubinemia (abnormally high level of bilirubin in the blood)
  • Certain medications (make sure to keep your physician up to date on all your current medications)

You might be asking, “What should I do with the above information?”

• First things first, talk with your physician.
• Ask your doctor about the A1c test. How often should you have the A1c test done and what is your A1c target (based on your current diabetes management)?
• If you A1c is above target, ask your physician about lifestyle changes (i.e. diet, exercise) that may help lower A1c and if/when medication is indicated (if you are already on medication a change may be necessary to help you reach your goal).