Hemoglobin A1c Test (HbA1c, A1c, Hb1c)

  • Medical Author:
    Ruchi Mathur, MD, FRCP(C)

    Ruchi Mathur, MD, FRCP(C) is an Attending Physician with the Division of Endocrinology, Diabetes and Metabolism and Associate Director of Clinical Research, Recruitment and Phenotyping with the Center for Androgen Related Disorders, Department of Obstetrics and Gynecology at Cedars-Sinai Medical Center.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Type 2 Diabetes: Learn the Warning Signs

What is a hemoglobin A1c?

To explain what an A1c is, think in simple terms. Sugar sticks, and when it's around for a long time, it's harder to get it off. In the body, sugar sticks too, particularly to proteins. The red blood cells that circulate in the body live for about three months before they die. When sugar sticks to these cells, it gives us an idea of how much sugar has been around for the preceding three months. In most labs, the normal range is 4-5.9 %. In poorly controlled diabetes, its 8.0% or above, and in well controlled patients it's less than 7.0%. The benefits of measuring A1c is that is gives a more reasonable view of what's happening over the course of time (3 months), and the value does not bounce as much as finger stick blood sugar measurements.

There is a correlation between A1c levels and average blood sugar levels as follows:

While there are no guidelines to use A1c as a screening tool, it gives a physician a good idea that someone is diabetic if the value is elevated. Right now, it is used as a standard tool to determine blood sugar control in patients known to have diabetes.

A1c(%) Mean blood sugar (mg/dl)
6 135
7 170
8 205
9 240
10 275
11 310
12 345

The American Diabetes Association currently recommends an A1c goal of less than 7.0%, while other groups such as the American Association of Clinical Endocrinologists recommend a goal of less than 6.5%.

Of interest, studies have shown that there is a 10% decrease in relative riskfor every 1% eduction in A1c. So, if a patients starts off with an A1c of 10.7and drops to 8.2, though there are not yet at goal, they have managed todecrease their risk of microvascular complications by about 20%. The closer to normal the A1c, the lower the absolute risk for microvascular complications.

Medically reviewed by Joseph Palermo, DO; American Osteopathic Board Certified Internal Medicine

REFERENCE:

National Diabetes Information Clearinghouse (NDIC)
http://diabetes.niddk.nih.gov/dm/pubs/A1CTest/

Medically Reviewed by a Doctor on 5/21/2015

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