How to Calculate Your A1C Levels [+Try our A1C Calculator]

If you’ve recently taken a blood test or you’ve been discussing glucose levels with your doctor, you may be familiar with the A1C test. While only a lab test can accurately measure your A1C value (otherwise known as HbA1C), it’s also possible to calculate a general estimate of your A1C.

The results may help provide an approximation of how much glucose has been in your bloodstream on average for the past two to three months. Why is it important to learn more about your A1C? For one, keeping track of your A1C can help you stay on top of your wellbeing. It may also be something your healthcare provider recommends paying more attention to if you’re at risk of developing type 2 diabetes.

In this article, we’ll give you a quick refresher on what exactly A1C is, and show you how to get a good estimate of yours with our handy A1C calculator.

What Does A1C Actually Measure?

The A1C test measures the amount of glucose bound to the hemoglobin (or glycated hemoglobin) in the blood over the months-long lifetime of your blood cells. In simpler terms: the A1C test is a way to measure your average blood glucose levels over time. 

An A1C test result will appear as a percentage, with normal levels considered to be below 5.7 percent. According to the CDC, having A1C values within this normal range may be able to help reduce your risk of diabetes.

An A1C value differs from the insight you would get from a glucometer or continuous glucose monitor. Measurements from these tools are reported in mg/dL or mmol/L, and measure the concentration of blood sugar in your bloodstream.

A tool such as a CGM can be helpful for recognizing instances of hypoglycemia (low blood sugar) as they occur, or hyperglycemia (high blood sugar) after eating a meal. 

The Difference Between Estimated Average Glucose (eAG) and A1C

A1C is a measurement of glycated hemoglobin, and is reported as a percentage of your average blood sugar level. 

Estimated average glucose (or eAG), on the other hand, is a value calculated from your A1C value and is measured in mg/dL or mmol/L.

For more information on what these values signify, read our article on normal blood sugar levels.

As we mentioned, your A1C value stems from the two or three months that your red blood cells are alive. Because A1C represents sugar levels over such a long period, your doctor can use this to get a general idea of your blood sugar control. 

However, it’s important to note that hemoglobin A1C is not a measure of the exact concentration of glucose in your blood. It is instead a measure of the percent of hemoglobin that has glucose bound to it.

While A1C can be a helpful tool to estimate how your blood sugar has been on average, there are some outside factors that may make it less accurate.

What is Estimated Average Glucose?

Like A1C, your estimated average glucose (or eAG) measures the average levels of your blood sugar over a few months. It’s convenient for those interested in learning about their blood sugar levels since eAG is a measurement of mg/dL or mmol/L, the same units used on any glucometer or CGM. 

You may have had your doctor explain your A1C levels in terms of estimated average glucose, or eAG. Estimated average glucose that falls below 126 mg/dL is considered normal by researchers and medical professionals. Just like with A1C, regularly checking your eAG may give you a more accurate representation of your blood sugar response over time. 

If your A1C or eAG is out of the normal range, you may want to speak with a doctor about what factors may be causing your elevated levels and how they may affect your well being. 

Simple Conversion Formula for A1C From Average Blood Glucose

Now that you know what A1C is and what it measures, here’s how you can calculate it using your average glucose level. Luckily, it’s fairly simple to estimate your A1C percentage using a formula no more complicated than converting Celsius to Fahrenheit.

Blood glucose is measured in different ways depending on where you live. In the United States, you’ll find levels measured in mg/dL, while other countries generally use mmol/L.

Remember, it’s only possible to see a rough estimate when calculating your A1C, as any calculator will use your eAG value to determine your A1C. It may be a good idea to speak with your doctor about getting a proper lab test if you’re concerned about your A1C. 

To calculate your A1C value, all you need to do is apply your average blood glucose measurement to one of the following formulas:

Try Our A1C Calculator

Not everyone loves crunching numbers, so if that formula is too much of a hassle, you can calculate an estimation of your A1C value using our handy A1C calculator. 

Now that you have your A1C value, let’s take a closer look at how you can understand your A1C calculation. Later on, we’ll explain a few other ways you can test your A1C, either in a lab or at home.

Understanding the Range of A1C

Now that you have an estimate of your A1C, check whether your levels are outside of the normal range by comparing your result to the ranges used by both the American Diabetes Association (ADA) and the CDC:

If your estimated range falls anywhere above 5.7 percent, you may want to visit your doctor to learn more about the factors that can affect your blood sugar response. One way to detect imbalances and fluctuations in glucose to see its impact on overall wellness is by using a tool such as a continuous glucose monitor. 

There are a number of lifestyle changes that may be beneficial as you work to lower your levels over time. Your doctor may also help you set an A1C goal to aim for.

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Ways to Calculate Your A1C

Using a 30, 60, or 90-day Average Glucose Value From a CGM

Most CGMs can provide you with an average of your glucose readings over a chosen period. Using the calculator or conversion formulas that we shared earlier in the article can help translate those averages into an A1C estimation.

Like with eAG, you’ll have to take the data points making up these averages routinely. If they're sporadic or have significant gaps, you could see an unreliable or inconsistent A1C measurement.

Calculating Your A1C From Your eAG

If you already know your eAG from a doctor's visit or another test, you can derive your A1C from the same calculator or formulas above. Remember, however, that this measurement is an estimation and if you find that your value is outside of the normal range, you may want to speak to your doctor to learn more.

A1C Home Tests

Options for telehealth and remote doctor visits have never been more popular. To meet the demand, many lab tests now have comparable analogs available to consumers. This includes at-home A1C tests, which can be just as accurate as lab tests prescribed by your doctor. 

While many are available at your pharmacy, some are only available to purchase online. Most are affordable, but costs can stack up with frequent testing if your insurance plan doesn’t cover home tests.

The bells and whistles can vary as much as cost, so we recommend shopping around to pick what’s best for you and your needs.

A1C Lab Tests

Lab tests are some of the most common ways to get A1C results. There’s the traditional route, with tests prescribed by a doctor, and there’s also on-demand lab tests where outside doctors sign off on the tests without direct consultation. 

Wherever you choose to get them, it may be a good idea to go over the results with a dietitian or doctor who knows your medical history. This way, they can advise you with your unique physiology in mind.