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Your Comprehensive Guide to A1C Levels and Testing

The A1C test provides a 3-month average of blood sugar levels, essential for diagnosing and managing diabetes or prediabetes. It measures the percentage of glycated hemoglobin, with results indicating normal levels, prediabetes, or diabetes. This test is convenient, requiring no fasting, and complements other health metrics for a comprehensive view of glucose management. Understanding and addressing factors affecting A1C accuracy ensures effective health monitoring and proactive diabetes care.

What is the A1C Test, and What Does it Measure?

If you have ever had a routine medical checkup that included blood tests, you may have come across a curious shorthand like “A1C” written on a lab order. Unlike a quick blood sugar check, which simply measures your glucose level at a single point in time, the A1C test takes a more panoramic view. Think of it as a long-term health tracker: it gathers information about your average blood sugar levels over the past three months.

Sometimes referred to as the HbA1C test, the A1C test is a laboratory test that provides an average reading of your blood sugar levels over approximately the past three months. It does this by examining a protein in your red blood cells called hemoglobin. Hemoglobin is responsible for carrying oxygen throughout your body, but it has a notable characteristic: it can become chemically bound to glucose (sugar) molecules floating around in your bloodstream. 

Two red and purple lipsticks on a white surface

This bond between hemoglobin and glucose is often referred to as “glycation.” The A1C test measures the percentage of hemoglobin that is “glycated”—in other words, how much of it is carrying extra sugar. 1 Since red blood cells live around 120 days, the A1C test effectively reveals an extended snapshot of your blood sugar levels. If you have high blood glucose for a prolonged period, more of your hemoglobin will become glycated, pushing your A1C percentage higher. Conversely, if your blood sugar tends to remain stable and within a healthy range, you will have a lower A1C.

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When Would I Need an A1C Test?

The A1C test is frequently used as a diagnostic and monitoring tool. If you have never been diagnosed with diabetes or prediabetes but have risk factors like a family history of diabetes, obesity, hypertension, or a sedentary lifestyle, your doctor might recommend an A1C test. This helps gauge whether your blood sugar control is inching into dangerous territory.

If you have already been diagnosed with diabetes, A1C testing typically becomes part of your ongoing care routine. People with diabetes often undergo this test a few times a year to evaluate how well their treatment plan is working. For example, you might be following a new diet, exercising more, or taking specific medications or insulin. Your healthcare provider uses the A1C results to see if these interventions are improving your long-term glucose management.

A1C is just part of your toolkit‎

It is essential to recognize that while the A1C test is a significant piece of the puzzle, it is not the only one. Daily blood sugar monitoring, continuous glucose monitors (if prescribed), and other tests such as fasting glucose or post-meal glucose checks all contribute valuable information. Additionally, factors like blood pressure, cholesterol, and body weight play into your overall metabolic health. A1C does not replace these measurements; rather, it complements them, giving you and your medical team a broader perspective. 2

Where can you get A1C test?

You can have your A1C test done at a medical laboratory, a doctor’s office, or even some pharmacies and clinics that offer on-site testing services. Some medical providers also utilize point-of-care tests, where you can get an A1C reading during a single office visit. Mail-in kits that allow you to send a small blood sample to a lab are also available, though it is generally recommended to have the test conducted by a healthcare professional to ensure accuracy and context for your results.

Understanding A1C Test Details

How is A1C calculated?

The A1C percentage represents the amount of hemoglobin that’s saturated with glucose. If, for example, your result is 6.5%, it means that out of all the hemoglobin in your red blood cells, about 6.5% has glucose attached. Laboratories rely on standardized chemical processes to isolate glycated hemoglobin and measure it accurately. 

There is also a related concept called eAG (estimated average glucose), which converts your A1C result into an approximate daily average blood sugar level. 3 This conversion can make results feel more relatable: an A1C of about 6% often corresponds to an average glucose level of roughly 126 mg/dL.

Do I need to fast for an A1C test?

No. One of the advantages of the A1C test is that you do not need to fast beforehand. Whereas traditional fasting blood glucose tests require you to abstain from eating for 8 to 10 hours, you can take the A1C test at any time of day, regardless of your recent meals. This convenience makes the A1C test a popular choice for initial screenings and ongoing diabetes management.

What should I expect during an A1C test?

The A1C test itself is fairly simple. A healthcare professional will draw a small vial of blood, usually from a vein in your arm. This sample is then sent to a lab for analysis, unless a point-of-care testing device is used, in which case the result might be available within minutes. The experience is like any routine blood draw: a bit of a pinch at the needle site, followed by mild soreness that typically subsides quickly.

What are the risks of an A1C test?

A1C testing is a low-risk procedure. The most common side effects are minor bruising or a small amount of bleeding at the puncture site. In rare cases, individuals might feel lightheaded or faint, but that is not unique to the A1C test—it can happen whenever blood is drawn. Overall, it is one of the safer and more straightforward lab tests available.

Results and Follow-Up

If your result is normal:

A normal A1C result is generally below 5.7%. If yours falls within this range, it implies that your blood sugar levels have been stable and well-managed over the past few months. 4 This good news suggests that you do not have diabetes or prediabetes. 

However, maintaining normal readings doesn’t mean you can ignore healthy habits. It is wise to continue focusing on a balanced diet, regular exercise, and routine medical check-ups. Preventive measures help ensure that these normal results continue well into the future.

If your result shows you have prediabetes:

If your A1C level comes back between 5.7% and 6.4%, it suggests that your body’s handling of glucose has begun to shift away from the ideal. While you haven’t crossed the threshold into diabetes, your blood sugar levels are higher than normal, indicating prediabetes. 4 Think of this as a critical early-warning sign and an opportunity to take decisive action before diabetes fully sets in. 

By interpreting this result not as a grim verdict but as a call to action, you can empower yourself to change course and foster habits that restore healthier glucose control.

Successfully managing prediabetes often involves gradually reshaping your daily routine. Sometimes, subtle adjustments—like cutting down on sweetened beverages or swapping out refined carbohydrates for whole grains—can produce noticeable benefits over time. 

girl doing yoga, relaxing

Increasing physical activity is a particularly powerful step: incorporating 30 minutes of moderate exercise most days can help improve insulin sensitivity and stabilize blood sugar.  Engaging the support of a healthcare professional or a registered dietitian can provide personalized guidance as they can help you prioritize improvements in areas like diet, weight management, and exercise strategies. In some cases, medication may be considered, but more often than not, lifestyle modification stands as the cornerstone of reversing prediabetes and preventing the progression to type 2 diabetes.

If your result shows you have diabetes:

When an A1C of 6.5% or higher appears on at least two separate tests, it typically indicates diabetes. 4 For many people, this news can feel overwhelming, but it is important to remember that a diagnosis is not a personal failing, nor is it the end of the road. Instead, it is a starting point for understanding your body’s unique challenges and learning how to manage them. You will work closely with your healthcare provider to develop a tailored treatment plan, which often includes medication, whether oral medications or insulin injections to help keep blood glucose levels in check. This plan will likely also encompass a balanced diet, regular exercise, and consistent follow-up tests, all designed to curb complications and maintain your quality of life.

The first few weeks and months after a diabetes diagnosis may feel like a period of intense learning, but you are not alone. Your medical team, which may include doctors, nurses, dietitians, and possibly diabetes educators, can help you navigate this unfamiliar territory. Over time, you can  develop a routine that balances nutrient intake, physical activity, medication timing, and regular blood glucose monitoring. 

Many individuals find success by embracing a holistic approach, incorporating stress-reduction techniques, making incremental lifestyle shifts, and leaning on friends, family, or support groups for encouragement. Although the road may require patience and adjustments, countless people live full, vibrant lives with diabetes, proving that managing this condition effectively and confidently is entirely possible.

What Does my A1C Mean?

What is a normal A1C?

A “normal” A1C is typically below 5.7%. In everyday terms, this number suggests that your blood sugar control over the last three months has been within a healthy, stable range. For someone without diabetes or with diabetes that is well-controlled, this range means your body is efficiently processing glucose.

What is a dangerous level of A1C?

While there’s no single number that suddenly becomes “dangerous,” complications from diabetes tend to increase as A1C levels rise. Levels above 9% generally ring alarm bells, especially for people with diabetes. Higher percentages often mean that you have been living with elevated glucose for a prolonged period, putting stress on various organs and systems. 5 Over time, chronic high blood sugar can cause problems with your eyes, kidneys, nerves, and cardiovascular system. 6 The higher the A1C, the greater the risk of complications, so your healthcare team will usually recommend strategies to bring it down and keep it as close to normal as possible.

Factors That Affect A1C Accuracy

While the A1C test is a valuable tool, it is not perfect. Various health conditions and factors can influence your A1C reading. Understanding these can help you and your healthcare provider interpret results more accurately.

Causes of falsely low A1C results

Sometimes, conditions that shorten the lifespan of red blood cells can lower your A1C, even if your average blood sugar is higher than ideal. For example, if you have hemolytic anemia, a condition where red blood cells break down faster than normal, you might have fewer older red blood cells for the test to measure. 

Because A1C relies on an average that includes older cells, fewer older cells can reduce the overall percentage of glycated hemoglobin. 7 Similarly, recent severe blood loss or donation, followed by a rapid production of new red blood cells, can lower A1C. These scenarios mean that despite having a high blood sugar level on a daily basis, your A1C might not reflect that accurately.

Causes of falsely high A1C results

On the flip side, some conditions prolong the lifespan of red blood cells or otherwise interfere with the way the test is measured. Certain forms of anemia (like those associated with low iron) can cause red blood cells to live longer, meaning older cells with more glucose buildup remain in circulation. This can lead to an artificially elevated A1C number. Kidney disease, some vitamin deficiencies, and thyroid disorders may also affect A1C accuracy. 8

Your ethnic background and genetic makeup can also influence how your hemoglobin behaves. In some populations, certain hemoglobin variants (like those associated with sickle cell trait) may skew A1C results. If your doctor suspects that your A1C is not providing a clear picture, they might use alternative tests, such as fructosamine tests, to better understand your average glucose control.

Can you Have a High A1C and not Have Diabetes?

It might sound counterintuitive, but yes, it is possible, although not very common. Sometimes, other health conditions unrelated to diabetes can cause elevated A1C levels. Chronic kidney disease, liver disease, or issues with the spleen can sometimes push A1C upward. Similarly, prolonged iron deficiency anemia can result in a higher A1C reading. This does not mean you have diabetes, but it does mean your doctor will want to investigate further.

A1C and estimated average glucose (eAG)

A helpful concept related to A1C is the estimated average glucose (eAG). The eAG translates your A1C percentage into an approximate daily blood sugar level. This makes it more intuitive: for example, if your A1C is 7%, your eAG might be around 154 mg/dL. This number feels more familiar if you have ever used a home glucose meter. 

However, remember that eAG is an average—your blood sugar may fluctuate significantly throughout the day. High swings and low dips might not fully show up in a single average number. 9 Still, the eAG gives a good ballpark figure to understand how your glucose has been trending over time.

Hemoglobin variants and A1C results

Not all hemoglobin is created equal. Genetic differences can lead to variations in your hemoglobin, sometimes affecting how it glycosylates (binds with glucose) or how it is measured in labs. One common variant is the sickle cell trait, which is more prevalent in certain ethnic groups. 10 Hemoglobin variants can make standard A1C tests less reliable, but there are alternative testing methods to ensure accurate readings. 

If your background or family history suggests you might have a hemoglobin variant, discuss this with your healthcare provider. They may choose a different test method, like a fructosamine test or specialized A1C assays that can account for variants, to ensure you get accurate information.

Conclusion

Managing one’s health is often like navigating a complex map: there are multiple routes, checkpoints, and markers. The A1C test is one such marker, a reliable compass pointing you toward the state of your long-term blood sugar control. For those at risk of diabetes, it can serve as an early warning system, alerting you to the need for preventive measures. For those with diabetes, it is an essential guide that helps you and your healthcare team refine treatments, adjust diet and exercise routines, and keep complications at bay.

Although the A1C test is a powerful and useful tool, remember that it is just one component of your broader health picture. Lifestyle factors, such as your diet, physical activity level, stress management, and other medical conditions, are all puzzle pieces contributing to the whole. If your A1C is not where you or your physician would like it to be, do not despair. Small, incremental changes can have a meaningful impact over time.

Above all, this information should inspire you to work closely with a qualified healthcare provider. Every individual’s health circumstances are unique, and what’s ideal for one person may not be the perfect target for another. A medical professional can help interpret your test results in the context of your overall health, personal history, and lifestyle. Armed with professional guidance, you can chart a sustainable path forward—one that keeps your blood sugar levels and your life on a stable, healthy course.

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References

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[3] Ahmed, Sayed, Alyafei F, De Sanctis, Soliman A, and Elgamal M. 2018. “Translating the HbA1c assay into estimated average glucose values in children and adolescents with type 1 diabetes mellitus.” Acta Biomedica 89 (S5): 22–26. ;

[4] American Diabetes Association. 2019. “6. Glycemic Targets: Standards of Medical Care in Diabetes—2019.” Diabetes Care 42 (Supplement_1): S61–70. ;

[4] American Diabetes Association. 2019. “6. Glycemic Targets: Standards of Medical Care in Diabetes—2019.” Diabetes Care 42 (Supplement_1): S61–70. ;

[4] American Diabetes Association. 2019. “6. Glycemic Targets: Standards of Medical Care in Diabetes—2019.” Diabetes Care 42 (Supplement_1): S61–70. ;

[5] Azhar, Saud, Fahd Zafar Khan, Shahmir Tariq Khan, and Bushra Iftikhar. 2022. “Raised Glycated Hemoglobin (HbA1c) Level as a Risk Factor for Myocardial Infarction in Diabetic Patients: A Hospital-Based, Cross-Sectional Study in Peshawar.” ;

[6] Kulkarni, Aditi, Archana R Thool, and Sachin Daigavane. 2024. “Understanding the Clinical Relationship Between Diabetic Retinopathy, Nephropathy, and Neuropathy: A Comprehensive Review.” Cureus, March.;

[7] Balen, Marica Jandrić, Vesna Lukenda, Ivan Jandrić, Antonija Raguž, Sidbela Zukanović, and Blaženka Miškić. 2012. “HbA1C - overall glycemia marker and hemolytic anemia indicator.” Medicinski Glasnik (Zenica) 9 (2): 406–8. ;

[8] Deepthi, Dasari Mani, Suresh Vaikkakara, Avinash Patil, Sandeep Ganta, Alok Sachan, Katakam Raghavendra, Vinapamula S Kiranmayi, and Amit Kumar Chowhan. 2021. “Effect of Correction of Hyperthyroidism with Anti-thyroid Drugs on the Glycated Hemoglobin in Non-diabetic Patients with Primary Hyperthyroidism.” International Journal of Endocrinology and Metabolism 19 (1).;

[9] Garg, Pinky, Karthikeyan Pethusamy, and Rajiv Ranjan. 2022. “Correlation between Estimated Average Glucose Levels Calculated from HbA1c Values and Random Blood Glucose Levels in a Cohort of Subjects.” Journal of Laboratory Physicians 15 (02): 217–23.;

[10] Lacy, Mary E., Gregory A. Wellenius, Anne E. Sumner, Adolfo Correa, Mercedes R. Carnethon, Robert I. Liem, James G. Wilson, et al. 2017. “Association of Sickle Cell Trait With Hemoglobin A1c in African Americans.” JAMA 317 (5): 507. ;