What is Hemoglobin A1C?
Hemoglobin A1C is the part of red blood cells responsible for carrying oxygen to all cells of the body. In all cells glucose attaches to hemoglobin. Hemoglobin A1C may also be referred to as HbA1C, A1C or glycated hemoglobin. Today, its most commonly called A1C.1
What is the A1C test and what does it measure?
The A1C test measures the overall control of glucose levels over the last three months. Think of it as a 24/7 video of all of the ups, downs and in between of glucose levels over this period of time.
A1C is used to measure glucose control over time. This is possible because the more glucose there is in the bloodstream, the more glucose attaches to hemoglobin in the cells. When people with diabetes measure their glucose with a blood glucose monitor or continuous glucose monitor, these results show their glucose level at that one point in time, not over a period of time. The use of A1C along with day to day glucose results should be used in tandem to manage diabetes and progress or change a management plan.
A1C has a strong correlation to the development of diabetes complications. Research has shown time and again that keeping A1C levels under control over the years; the more likely it is that diabetes complications can be prevented or delayed.
How is A1C result reported?
A1C is reported as a percentage. An example is 7.5%.
What’s the recommended A1C for people with diabetes?
The American Diabetes Association (ADA) recommends an A1C goal of <7% in most adults (not pregnant), however some healthcare providers may recommend an A1C of <6.5% if the goal can be achieved and maintained without adverse effects or events, such as frequent hypoglycemia.2 On the converse an A1c of <8% is thought to be appropriate for people with a history of hypoglycemia (low glucose levels), limited life expectancy, advanced complications or other complexities of life.2
How often should A1C be measured in people with diabetes?
The ADA recommends that people who are meeting their treatment goals and have stable glucose control get their A1C checked at least two times a year. People who are not meeting their treatment goals should have their A1c checked quarterly.2
Is there a relationship between A1C and glucose control?
This table shows how to relate an A1C test result to an estimate of average glucose levels. Understanding this relationship can help people and their providers set realistic glucose targets based on their A1C goals. The last column shows that each A1C result has a large range, for example, an A1C of 7.0% may be closer to an estimated average glucose of 123, whereas an A1C of 7.9% may be closer to 180.2,3
Relate A1C Results to Glucose Levels
|A1C (%)||Estimated Average Glucose (mg/dL)||Glucose Levels Between (mg/dL)|
|6||126||100 – 152|
|7||154||123 – 185|
|8||183||147 – 217|
|9||212||170 – 249|
|10||240||193 – 282|
|11||269||217 – 314|
|12||298||240 – 347|
Is the A1C test accurate for everyone?
The A1C test has been available for about 40 years and it has become, along with self-glucose measures, a common way for people and their providers to follow overall glucose control over the past three months. However, in the last several years two questions have been raised about the potential limitations of A1C.
The first limitation focuses on accuracy. The A1C test may not be accurate for some people including people of African-American descent and people with liver and kidney disease, some anemias and sickle cell disease.
The second limitation is that while A1C offers an overall picture of glucose control, it doesn’t provide a detailed perspective. Glucose results, if in sufficient numbers, show the daily ups and downs and so-called patterns of glucose control. More informed observations and possible treatment changes to a person’s care plan can be made more accurately with both A1C and glucose results in hand.
There are an increasing number of mobile apps and digital health tools that help people track and analyze their glucose results. BlueStar, powered by Welldoc, is an FDA-cleared proven app for people with type 2 diabetes that allows people with type 2 diabetes to input their glucose results, communicate with their provider on demand and much more.
Can A1C be used to diagnose prediabetes and diabetes?
Since 2010 ADA has endorsed the use of the A1C test to diagnose prediabetes and diabetes.4 It has some advantages, such as greater convenience and less day-to-day variation of point in time glucose values. It also has several disadvantages, one being lower sensitivity.
The table provides the A1C levels at which prediabetes and diabetes can be diagnosed.1
|Prediabetes||5.7 – 6.4%|
|Diabetes (type 1 or 2)||6.5% or above|
Why is Keeping A1C in a healthy zone so important in diabetes care?
Numerous studies conducted over the last several decades conclude that achieving and maintaining A1C results within the desired range (see answer to What’s the recommended A1C for people with diabetes?) can help prevent and/or delay the common and costly complications of diabetes. These include: high blood pressure, decreased circulation, heart attacks, strokes, diminished sight or blindness, nerve damage to one or more areas of the body and more.2
How Does Control of A1C relate to cost of diabetes care?
The economic costs of diabetes are staggering. Recently the ADA published the latest of their quinquennial analyses. They showed total estimated costs of $327 billion with $237 billion on direct costs and $90 billion in indirect costs.5 For more details read this Insights “Reflections on the Staggering 2017 Economic Cost of Diabetes in U.S.”
Data from numerous studies show that better A1C demonstrates lower total healthcare costs. The introduction to a recent study on the estimated cost-effectiveness of implementing an intensive program of care for adults with type 2 diabetes provides a review of several studies.6 A study using claims data from a large health maintenance organization showed that the group of mainly type 2 patients whose A1C was lowered by 1% experienced lower total health care costs in the range of $685 to $950 less per year compared to people who had no A1C improvement. Another analysis from a large managed care organization showed that total diabetes-related costs for people whose A1C was greater than 7% was $1,540 per patient during the 1-year follow-up. This was 32% higher than the total diabetes-related costs ($1,171) for people whose A1C was at or below 7%.
Recently Truven Health Analytics®, part of the IBM Watson Health™ business, conducted an analysis for Welldoc using the MarketScan® Research Databases. These extensive databases include large employers, managed care organizations, hospitals, EMR providers and Medicare and Medicaid programs. Truven utilized data from two randomized control trials showing BlueStar’s ability to lower and control A1C by 1.7 to 2.0%.7,8 Truven Health researchers created a complex custom algorithm and applied it to the MarketScan data, resulting in quantified total costs broken down by A1C levels in a way that was comparable between ages, stability and degree of glycemic control. The data showed that the implementation of BlueStar in a population of people with type 2 diabetes can save, on average, a range of $254 to $271 per user per month .9
- Section 1The A1C Test & Diabetes. https://www.niddk.nih.gov/health-information/diabetes/overview/tests-diagnosis/a1c-test (Accessed April 25, 2018).
- Section 2American Diabetes Association. 6. Glycemic targets: Standards of Medical Care in Diabetes -2018. Diabetes Care.2018;41(Supp 1):S55-S64.
- Section 3National Glycohemoglobin Standardization Program (NGSP). Harmonizing Hemoglobin A1c Testing. 2010 http://www.ngsp.org/A1ceAG.asp. (Accessed April 25, 2018).
- Section 4American Diabetes Association. 2. Classification and diagnosis of diabetes: Standards of Medical Care in Diabetes -2018. Diabetes Care.2018;41(Supp 1):S55-S64.
- Section 5American Diabetes Association. Economic Costs of Diabetes in the U.S. in 2017. Diabetes Care. 2018;41(5):917-928.
- Section 6Hirsch JD, et al. Estimated Cost-Effectiveness, Cost Benefit, and Risk Reduction Associated with an Endocrinologist-Pharmacist Diabetes Intense Medical Management “Tune-Up” Clinic. J Manag Care Spec Pharm. 2017;23(3):318-326. https://www.jmcp.org/doi/full/10.18553/jmcp.2017.23.3.318. (Accessed April 25, 2018)
- Section 7Quinn C, Shardell M, Terrin M, et al. Cluster-randomized trial of mobile phone personalized behavioral intervention of blood glucose control. Diabetes Care 2011;34(9);1933-1943.
- Section 8Quinn C, Clough SS, Minor JM, et al. Welldoc™mobile diabetes management randomized controlled trial: change in clinical and behavioral outcomes and patient and physician satisfaction. Diabetes Technol Ther 2008;10(3);160-168.
- Section 9Welldoc validates potential of its digital therapeutic, BlueStar®, to significantly reduce healthcare costs. https://www.welldoc.com/images/uploads/Welldoc-Truven-Release.pdf. (Accessed April 25, 2018).