A1c guidelines have changed multiple times over the past three decades, with the most significant shift occurring in January 2010, when the American Diabetes Association first approved A1c as a standalone diagnostic test for diabetes. Before that, A1c was only used to monitor blood sugar over time, not to diagnose the disease. But the story of guideline changes goes well beyond that single moment, touching treatment targets, pediatric care, and how doctors think about A1c goals for different patients.
Before 2010: Diagnosis Without A1c
For decades, diagnosing diabetes meant measuring blood sugar directly. The World Health Organization proposed the first widely accepted lab standard in 1965, defining diabetes as a blood glucose level at or above 150 mg/dl two hours after drinking a sugary solution. In 1997, the ADA lowered the fasting blood sugar threshold from 140 to 126 mg/dl because this cutoff better matched the results of the oral glucose tolerance test. Fasting blood sugar became the preferred diagnostic method simply because it was easier for patients than sitting in a lab for two hours.
Throughout this period, A1c existed as a monitoring tool. Doctors used it to see how well a patient’s blood sugar had been controlled over the previous two to three months. But it wasn’t considered reliable enough for diagnosis because different labs produced inconsistent results for the same blood sample.
1996: Standardizing the Test
A key behind-the-scenes change happened in 1996, when the National Glycohemoglobin Standardization Program (NGSP) launched to make A1c testing consistent across laboratories. Before this program, an A1c of 7% at one lab might not mean the same thing at another. The NGSP gave labs a common reference point, and over the following decade, A1c results became reliable enough that experts began considering the test for diagnosis.
2010: A1c Becomes a Diagnostic Tool
In January 2010, the ADA published revised diagnostic criteria that added A1c at or above 6.5% as a way to diagnose diabetes. This was a major shift. For the first time, a doctor could diagnose diabetes without requiring a fasting blood draw or a glucose tolerance test. The A1c test uses a simple, non-fasting blood sample and reflects average blood sugar over roughly three months rather than a single snapshot.
The WHO followed in 2011, endorsing the same 6.5% cutoff for international use. The current diagnostic ranges, which have remained stable since then, break down as follows:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
The ACCORD Trial and the Shift Away From Aggressive Targets
While the diagnostic cutoffs were being established, a separate and equally important guideline change was happening around treatment targets. For years, the prevailing wisdom was that lowering A1c as much as possible would prevent heart attacks and strokes in people with type 2 diabetes. The ACCORD trial tested this directly, assigning some patients to push their A1c below 6.0% (near-normal levels) while others aimed for 7.0% to 7.9%.
The results, published in 2008, were sobering. After 3.5 years, the group aggressively lowering their blood sugar had a higher death rate than the group with more moderate targets. The intensive approach did not significantly reduce heart attacks or strokes. This was a turning point. Guidelines shifted away from a one-size-fits-all push toward the lowest possible A1c and toward individualized targets that weigh a patient’s age, overall health, and risk of dangerous blood sugar lows.
Individualized Targets Replace Universal Goals
The ACCORD findings reshaped how the ADA frames A1c goals. Current guidelines recommend an A1c below 7% for most adults with diabetes, but they explicitly allow for less aggressive targets. For patients with limited life expectancy, a long history of diabetes, or conditions where blood sugar drops could be dangerous, an A1c goal below 8% may be more appropriate. The idea is that pushing too hard to lower A1c can cause severe hypoglycemia, which carries its own serious risks including falls, confusion, and cardiac events.
The 2022 Standards of Care formalized this with a framework asking doctors to reassess A1c targets regularly based on each patient’s changing health. The 2025 Standards further refined this, adding a specific decision-making tool to help set glycemic goals based on a person’s health status, treatment burden, and risk of complications.
Pediatric Targets: Lowered in 2020
Children with type 1 diabetes had their own distinct A1c history. For years, the ADA recommended different targets for different age groups, with higher A1c goals for younger children out of concern that aggressive blood sugar control would cause dangerous lows. In 2015, the ADA simplified this to a single target of below 7.5% for all pediatric age groups.
In 2020, the ADA lowered the pediatric target again, to below 7% for many children, matching the adult goal. This change was driven by several factors: newer insulins and technologies like continuous glucose monitors had made tighter control safer, the overall rate of severe hypoglycemia in children had dropped, and research continued to show that prolonged high blood sugar in childhood causes lasting damage to blood vessels and the brain. The 2025 Standards went further for children with type 2 diabetes specifically, recommending an even tighter A1c goal of below 6.5% because these patients face a lower risk of hypoglycemia and a higher risk of complications.
Continuous Glucose Monitors and “Time in Range”
The most recent evolution in A1c guidelines isn’t about changing the number itself. It’s about supplementing A1c with new metrics. Continuous glucose monitors (CGMs) track blood sugar every few minutes, generating data that A1c alone can’t capture. Two people with identical A1c results can have very different daily experiences: one might have stable blood sugar while the other swings between dangerous highs and lows that average out to the same number.
Starting with the 2023 Standards of Care, the ADA began recommending that doctors assess glycemic status using “A1c or other glycemic measurement such as time in range.” Time in range measures the percentage of the day a person’s blood sugar stays between 70 and 180 mg/dl. The 2025 Standards expanded this further, incorporating time in range and time below range into specific treatment goals for older adults. For patients using CGMs, guidelines now emphasize looking at mean glucose, trends, and overall patterns rather than relying on A1c alone.
When A1c Can Be Misleading
One important and often overlooked guideline detail: A1c doesn’t work reliably for everyone. The test measures how much sugar is attached to hemoglobin in red blood cells, so any condition that changes red blood cell lifespan or hemoglobin structure can throw off results. People with sickle cell disease, other hemoglobin variants, significant kidney disease, liver failure, or certain types of anemia may get falsely high or low A1c readings depending on the testing method used. For these patients, guidelines direct doctors to rely on direct blood sugar measurements or CGM data instead. The 2025 ADA Standards added a new reference table specifically addressing how to interpret A1c results when these conditions are present.