For monitoring purposes, the way that the A1c is reported is in the process of changing. Traditionally, in the United States, the A1c has been reported as a percentage, and the American Diabetes Association (ADA) has recommended that people with diabetes strive to keep their A1c below 7%. While this is still generally true, more than a decade of national and international efforts to improve and standardize the A1c test and its reporting led to the release of a consensus statement in 2007 (and an update in 2010) by the ADA, the European Association for the Study of Diabetes (EASD), the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), the International Society for Pediatric and Adolescent Diabetes, and the International Diabetes Federation. These joint statements and the completion of a study called ADAG (A1c-Derived Average Glucose) that further examined the relationship between blood glucose concentrations and A1c led to a recommendation that A1c be reported worldwide in two ways:
• As a percentage (based upon National Glycohemoglobin Standardization Program (NGSP) derived units) and
• In SI (Système International) units (mmol/mol)
An estimated Average Glucose (eAG) based upon a formula developed from the ADAG study with either mg/dL or mmol/l as units that continue to be recognized by the ADA and the American Association for Clinical Chemistry in the 2015 ADA Diabetes Care Position Statement may also be reported.
What this means for diabetics and health practitioners in the U.S. is that A1c results will be reported as a percentage but may in addition to this be reported as mmol/mol and, in some cases, also as an eAG with the same type of units (mg/dL) as are reported by home glucose monitors and laboratory results.
Yes. If you have already been diagnosed with diabetes, a home test may be used to help monitor your glucose control over time. However, a home test (point-of-care test) is not recommended for screening or diagnosing the disease. There are FDA-approved tests that can be used at home. If you are interested in learning more, visit the article on Home Tests and ask your healthcare provider.
Beyond the difference in units used to report them, the A1c represents an average over time while your blood glucose reflects what is happening in your body now. Your blood glucose will capture the changes in your blood sugar that occur on a daily basis, the highs and the lows. Each blood glucose is a snapshot and each is different. The A1c is an indication that "in general" your glucose has been elevated over the last few months or "in general" it has been normal. It is inherently not as sensitive as a blood glucose. However, if your day-to-day glucose control is stable (good or bad), then both the A1c and blood glucose should reflect this. It is important to remember the time lag associated with the A1c. Good glucose control for the past 2-3 weeks will not significantly affect the A1c result for several more weeks.
In addition to this, it is also important to remember that glycated hemoglobin and blood glucose are two different but related things. For unknown reasons, some peoples' A1c may not accurately reflect their average blood glucose.
This article was last reviewed on September 4, 2015. | This article was last modified on September 4, 2015.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
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