HbA1c (Hemoglobin A1c): Is This Test Reliable?

by Cindy

The hemoglobin A1c (HbA1c) is a powerful monitoring tool used by physicians to track your blood sugar over the course of 3 months.  This simple blood test is widely used for diagnosing diabetes and for monitoring average blood sugar levels.   For information about how the HbA1c test is used to diagnosis and monitor diabetes, click here!

Your physician will check your hemoglobin A1c every 3-6 months depending on how well your diabetes is controlled.  Based on these readings, your physician will recommend dietary changes, medications and follow up blood work.  With so much determined by one simple test it is important to know, is the HbA1c test reliable?

Remember that the HbA1c blood test is a measure of the average amount of glucose in your blood over a 2-3 month period.  Prior to standardization of laboratory values nationally, the accuracy of this test was dependent on the laboratory in which it was conducted.  With new guidelines in place, the accuracy of this test has improved significantly. 

Important points to note about the accuracy of the hemoglobin A1c test include:

  • There tends to be a margin of error of ±0.5%.  This means that if your HbA1c is reported to you as 8.0%, based on the margin of error your reading is between 7.5% and 8.5%.  To correlate these values with your average glucose reading in mg/dl check out our calculator!
  • Specimens that are not processed correctly can be less accurate.
  • This testing is less reliable in patients with certain blood conditions, such as sickle cell disease, thalassemia or severe anemia. Recent blood transfusions will also skew results.
  • Patients with iron deficiency may experience falsely elevated HbA1c readings.
  • Patients who have abnormal hemoglobin, hemoglobin variant, may have inaccurate readings due to interference of the variant hemoglobin with the testing.  If you have variant hemoglobin, it is important that your physician send your blood to certified labs that use methods that are not influenced by your particular condition.

For the most consistent results, it is best to visit the same lab every time that your blood work is done.  If your home glucose readings do not seem to correlate with your hemoglobin a1c results, it is important to let your doctor know and perhaps even repeat the testing.

photo by: Amy Loves Yah

Previous post:

Next post: