What Should You Do With Your A1C Results?
Review your A1C results with your healthcare team to determine if your current management plan is working or needs adjustment. An A1C at or below your individual target indicates good control — maintain your current approach. An A1C above target calls for evaluating medication, diet, exercise, and monitoring adherence, and making specific adjustments with clear follow-up timelines.
Your A1C result is not just a number — it is a management tool that guides treatment decisions. If your A1C is at or below your individual target (below 7 percent for most adults), your current combination of medication, diet, and activity is working well. Continue your current plan, maintain regular monitoring, and schedule your next A1C test as recommended (typically in 6 months). If your A1C is above target, work with your healthcare team to identify the cause: Are you taking medications consistently? Has your diet changed? Are you getting enough physical activity? Is stress or illness affecting your glucose? Are your medications still adequate?
For every A1C above target, the ADA recommends a structured approach to intensification. If A1C is 0.5 to 1.0 percentage point above target, lifestyle modifications and medication adherence should be reinforced, with reassessment in 3 months. If A1C is more than 1.0 to 1.5 percentage points above target, medication adjustment or addition is typically needed. The ADA and EASD consensus report provides a decision pathway for choosing second-line agents based on cardiovascular disease status, kidney health, weight management needs, and hypoglycemia risk. Recheck A1C 3 months after any therapy change to assess the impact.
The ADA recommends reevaluating therapy and potentially intensifying treatment when A1C is above the individualized target
How Does the A1C Test Work?
The A1C test measures the percentage of hemoglobin in red blood cells that has glucose permanently attached to it (glycated hemoglobin). Because red blood cells live approximately 120 days, A1C reflects the average blood sugar over the preceding 2 to 3 months, with more recent weeks weighted more heavily due to the continuous turnover of red blood cells.
Hemoglobin is the oxygen-carrying protein inside red blood cells. When blood glucose is elevated, glucose molecules attach to hemoglobin through a non-enzymatic process called glycation. Once attached, the glucose remains bonded to hemoglobin for the lifespan of the red blood cell (approximately 120 days). The higher the average blood glucose, the greater the percentage of hemoglobin that becomes glycated. An A1C of 6 percent means that approximately 6 percent of hemoglobin molecules have glucose attached, corresponding to an estimated average glucose of about 126 mg/dL. An A1C of 7 percent corresponds to approximately 154 mg/dL, and 8 percent corresponds to approximately 183 mg/dL.
The A1C test is performed using a small blood sample, either from a vein draw or a finger-stick point-of-care device. Laboratory A1C testing uses high-performance liquid chromatography or immunoassay methods standardized to the DCCT reference assay. Point-of-care A1C devices available in many clinics provide results in minutes, allowing treatment decisions during the same visit. The ADA recommends that point-of-care devices be NGSP-certified to ensure accuracy. Unlike fasting glucose or oral glucose tolerance tests, A1C does not require fasting, making it convenient for both patients and providers.
What Do A1C Numbers Mean?
Normal A1C is below 5.7 percent. Prediabetes is diagnosed at 5.7 to 6.4 percent. Diabetes is diagnosed at 6.5 percent or higher. For people with diabetes, the ADA recommends a treatment target below 7 percent for most adults, though individual targets may be more or less stringent based on clinical factors.
The relationship between A1C and average glucose has been precisely quantified through studies using continuous glucose monitoring. The ADAG (A1C-Derived Average Glucose) study established the conversion: A1C 5 percent equals approximately 97 mg/dL average glucose; 6 percent equals 126 mg/dL; 7 percent equals 154 mg/dL; 8 percent equals 183 mg/dL; 9 percent equals 212 mg/dL; and 10 percent equals 240 mg/dL. Many laboratory reports now include the estimated average glucose (eAG) alongside the A1C percentage to make results more intuitive for patients.
Individualized A1C targets are critical. The ADA recommends below 7 percent for most adults, which has been shown by the DCCT and UKPDS to reduce microvascular complications. More stringent targets of below 6.5 percent are reasonable for patients with short diabetes duration, long life expectancy, no significant cardiovascular disease, and low hypoglycemia risk. Less stringent targets of below 8 percent are appropriate for patients with history of severe hypoglycemia, hypoglycemia unawareness, limited life expectancy, extensive comorbid conditions, or long-standing diabetes with established complications. The ACCORD trial demonstrated that aggressively targeting A1C below 6 percent in high-risk type 2 diabetes patients increased mortality, reinforcing the importance of individualized goals.
The ACCORD trial showed that targeting A1C below 6 percent in high-risk patients increased mortality, reinforcing individualized goal-setting
What Factors Can Affect A1C Accuracy?
Several conditions can make A1C results inaccurate. Anything that changes red blood cell lifespan or hemoglobin structure can alter A1C independently of actual glucose levels. Hemoglobin variants, iron deficiency anemia, chronic kidney disease, pregnancy, recent blood transfusion, and certain medications can all affect A1C accuracy.
Conditions that prolong red blood cell lifespan cause falsely elevated A1C because hemoglobin has more time to accumulate glucose. Iron deficiency anemia, vitamin B12 deficiency, and splenectomy all prolong red blood cell survival and can raise A1C by 0.5 to 1.0 percentage point above the true value. Conversely, conditions that shorten red blood cell lifespan cause falsely low A1C: hemolytic anemias, recent significant blood loss, blood transfusions, erythropoietin therapy, and the second and third trimesters of pregnancy all reduce A1C below the true glucose average.
Hemoglobin variants, including sickle cell trait (hemoglobin AS), hemoglobin C trait, and thalassemia trait, can interfere with certain A1C assay methods. These variants are more common in African American, Mediterranean, and Southeast Asian populations. The NGSP maintains a list of A1C assays and their susceptibility to hemoglobin variant interference. When A1C is unreliable, alternative glycemic markers include fructosamine (reflecting 2 to 3 week average), glycated albumin (reflecting 2 to 3 week average), and continuous glucose monitoring metrics including time in range and glucose management indicator. The ADA recommends considering these alternatives when A1C and blood glucose data are discordant.
How Can You Lower Your A1C?
Lowering A1C requires a consistent combination of medication adherence, dietary improvements, regular physical activity, and blood sugar monitoring. Metformin alone reduces A1C by 1.0 to 1.5 points; GLP-1 agonists like semaglutide reduce it by 1.0 to 1.8 points. Lifestyle changes can reduce A1C by 0.5 to 2.0 points. Work with your healthcare team to create a personalized plan.
Medication adherence is the foundation of A1C improvement. Studies consistently show that one-third to one-half of people with diabetes do not take medications as prescribed, which is the most common reason for failing to reach A1C targets. Strategies to improve adherence include using pill organizers or smartphone reminders, simplifying regimens when possible (once-daily medications, combination pills), addressing side effects proactively, and understanding the purpose and importance of each medication. If cost is a barrier, discuss generic alternatives, patient assistance programs, or therapeutic substitutions with your healthcare team.
Dietary and activity changes complement medication therapy. Medical nutrition therapy from a registered dietitian reduces A1C by 0.5 to 2.0 percentage points. The most impactful dietary changes include eliminating sugar-sweetened beverages, reducing refined carbohydrate portions, using the diabetes plate method, and eating vegetables and protein before carbohydrates. Physical activity of at least 150 minutes per week of moderate-intensity exercise reduces A1C by approximately 0.66 percentage points. Even short walking breaks of 2 to 5 minutes every 30 minutes of sitting have been shown to improve postprandial glucose. Combining aerobic exercise with resistance training produces the greatest A1C improvements.
How Does A1C Compare to Time in Range?
A1C and time in range (TIR) are complementary metrics. A1C provides a 2 to 3 month average but misses glucose variability and hypoglycemia. TIR from continuous glucose monitoring shows the percentage of time glucose stays between 70 and 180 mg/dL, revealing patterns that A1C cannot capture. Each 10 percent increase in TIR correlates with approximately 0.5 percent lower A1C.
Two people can have identical A1C values but very different glucose profiles. Person A might have stable glucose around 154 mg/dL most of the time (A1C 7 percent, TIR 90 percent). Person B might swing between 60 and 300 mg/dL frequently, averaging out to the same 154 mg/dL (A1C 7 percent, TIR 40 percent). Person B has much higher complication risk despite the same A1C. TIR captures this critical difference. The international consensus on CGM metrics recommends targeting TIR above 70 percent (more than 16 hours and 48 minutes per day in 70 to 180 mg/dL range), with time below range less than 4 percent and time above range less than 25 percent.
Research increasingly shows that TIR is independently associated with diabetes complication risk. A study in Diabetes Care found that each 10 percentage point decrease in TIR was associated with a 64 percent higher risk of retinopathy progression. The glucose management indicator (GMI), calculated from CGM data, provides an estimated A1C that can be compared with laboratory A1C. When GMI and laboratory A1C differ significantly, it may indicate conditions affecting A1C accuracy or recent rapid changes in glycemic control. The ADA now recommends incorporating TIR metrics alongside A1C for a more complete picture of glycemic management.
A Diabetes Care study found that each 10 percentage point decrease in TIR was associated with 64 percent higher risk of retinopathy progression
When Should You Get Your A1C Tested?
Get A1C tested at least twice yearly if you are meeting treatment goals, and quarterly if your therapy has changed or you are not meeting targets. The ADA also recommends A1C for initial diabetes screening starting at age 35, with earlier screening if you have risk factors. Additional testing may be needed during pregnancy or acute illness.
The timing of A1C testing should align with your management needs and treatment adjustments. After starting a new medication or changing doses, allow 3 months before rechecking A1C to see the full effect. If you have made significant lifestyle changes, a 3-month recheck provides feedback on whether those changes are producing measurable results. During pregnancy in women with pre-existing diabetes, A1C should be checked monthly during the first two trimesters and as needed in the third trimester, with a target of below 6.0 to 6.5 percent to minimize birth defect and complication risk.
Point-of-care A1C testing, available in many primary care and endocrinology offices, provides results in minutes during your appointment. This allows immediate discussion of results and real-time treatment decisions rather than waiting days for laboratory results and a follow-up call. The ADA recommends using NGSP-certified point-of-care devices and periodically comparing their results with laboratory testing to ensure accuracy. Home A1C test kits are available over the counter but should not replace regular laboratory testing. They can be useful for interim monitoring between office visits, particularly for patients who have difficulty accessing healthcare frequently.
The ADA recommends A1C testing at least twice yearly for patients meeting goals and quarterly for those not meeting targets or with therapy changes
