All About Hemoglobin A1C

All About Hemoglobin A1C

What Is Hemoglobin A1C?

Hemoglobin is well known as the iron-containing metalloprotein found in red blood cells that helps transport oxygen in the body.1 Hemoglobin that has become glycosylated, or coated with glucose, in the presence of elevated intracellular glucose levels is commonly referred to as hemoglobin A1C.2


What Is the A1C Test?

The A1C test reflects the average glycemia over approximately 3 months and is used as the primary tool for assessing glycemic control and as a strong predictor of future diabetic complications.3 The American Diabetes Association (ADA) recommends testing A1C levels at initial diabetes assessment and routinely every 3 months to determine whether glycemic targets are reached and maintained in diabetic patients. The test requires a blood sample and is usually analyzed in a laboratory.1 The test will give its results in percentages, which corresponds to the average glucose levels experienced over the past 90 days.1,4


Relationship Between A1C and Glucose Levels
A1C % Estimated Average Glucose (mg/dL)
6 126
7 154
8 183
9 212
10 240


What Is a Good A1C Range?

Along with fasting plasma glucose levels, 2-hour plasma glucose values, and the oral glucose tolerance test, the A1C test can be used to diagnose diabetes.5 Individuals with normoglycemia have A1C levels below 5.7%. Individuals with levels between 5.7% and 6.4% are diagnosed with prediabetes, and individuals with levels equal to or above 6.5% are diagnosed with diabetes.

A1C Test*
Result A1C (%)
Normoglycemia <5.7
Prediabetes 5.7-6.4
Diabetes >6.5


*The A1C test should be performed in a lab that is National Glycohemoglobin Standardization Program (NGSP) certified and standardized to the Diabetes Control and Complications Trial (DCCT) assay.

Glycemic targets should be individualized based on patient’s specific needs, risks, and preferences. For most nonpregnant adults with diabetes, the 2021 ADA guidelines recommend an A1C goal of <7%. Epidemiological analyses of trials on intensive treatment suggest that aiming for lower A1C levels may be beneficial especially in individuals with long life expectancy and with low risk of hypoglycemia.6,7 Less stringent goals (<8%) may be more appropriate in individuals with limited life expectancy or when the risk of treatment is deemed greater than its benefit.3


How Do I Lower My A1C Levels?

Several studies have demonstrated that a strong and continuous association exists between A1C levels and subsequent diabetes.8–12 Additionally, achieving and maintaining A1C levels of <7% early in the disease progression have shown to decrease diabetes-related microvascular complications.3 As such, achieving A1C goals is important in not only managing diabetes but also minimizing long-term comorbidities.

The ADA strongly recommends making significant lifestyle changes including eating a healthy diet and exercising for all individuals with type 2 diabetes mellitus.2,3 Weight loss is also recommended for those who are overweight or obese. In most cases, pharmacological interventions used early in the disease progression can facilitate achieving glycemic target and mitigate microvascular and cardiovascular complications. For individuals with near-target A1C levels (ie, <7.5%) and who are highly motivated, pharmacotherapy can be delayed for 3-6 months to assess the effectiveness of lifestyle modification on glycemic control.


1. Eyth E, Naik R. Hemoglobin A1C. In: StatPearls. StatPearls Publishing; 2022. Accessed October 5, 2022.
2. Gallagher EJ, Le Roith D, Bloomgarden Z. Review of Hemoglobin A1c in the Management of Diabetes. Journal of Diabetes. 2009;1(1):9-17. doi:10.1111/j.1753-0407.2009.00009.x
3. American Diabetes Association. 6. Glycemic Targets: Standards of Medical Care in Diabetes—2021. Diabetes Care. 2020;44(Supplement_1):S73-S84. doi:10.2337/dc21-S006
4. CDC. All About Your A1C. Centers for Disease Control and Prevention. Published August 21, 2018. Accessed October 5, 2022.
5. American Diabetes Association. 2. Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes-2021. Diabetes Care. 2021;44(Suppl 1):S15-S33. doi:10.2337/dc21-S002
6. Diabetes Control and Complications Trial Research Group, Nathan DM, Genuth S, et al. The Effect of Intensive Treatment of Diabetes on the Development and Progression of Long-term Complications in Insulin-Dependent Diabetes Mellitus. N Engl J Med. 1993;329(14):977-986. doi:10.1056/NEJM199309303291401
7. Adler AI, Stratton IM, Neil HA, et al. Association of Systolic Blood Pressure With Macrovascular and Microvascular Complications of Type 2 Diabetes (UKPDS 36): Prospective Observational Study. BMJ. 2000;321(7258):412-419. doi:10.1136/bmj.321.7258.412
6. Zhang X, Gregg EW, Williamson DF, et al. A1C Level and Future Risk of Diabetes: A Systematic Review. Diabetes Care. 2010;33(7):1665-1673. doi:10.2337/dc09-1939
9. Selvin E, Steffes MW, Zhu H, et al. Glycated Hemoglobin, Diabetes, and Cardiovascular Risk in Nondiabetic Adults. N Engl J Med. 2010;362(9):800-811. doi:10.1056/NEJMoa0908359
10. Ackermann RT, Cheng YJ, Williamson DF, Gregg EW. Identifying Adults at High Risk for Diabetes and Cardiovascular Disease Using Hemoglobin A1c: National Health and Nutrition Examination Survey 2005–2006. Am J Prev Med. 2011;40(1):11-17. doi:10.1016/j.amepre.2010.09.022
11. Diabetes Prevention Program Research Group. HbA1c as a Predictor of Diabetes and as an Outcome in the Diabetes Prevention Program: A Randomized Clinical Trial. Diabetes Care. 2014;38(1):51-58. doi:10.2337/dc14-0886
12. Glauber H, Vollmer WM, Nichols GA. A Simple Model for Predicting Two-Year Risk of Diabetes Development in Individuals With Prediabetes. Perm J. 2018;22:17-050. doi:10.7812/TPP/17-050



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