NutriSense Blog

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

October 15, 2021
Reviewed By
Kara Collier, RDN, LDN, CNSC

Do you feel overwhelmed by the jargon and measurements involved in controlling your blood sugar? It can be challenging to keep track of everything, especially if you’re already preoccupied with a diabetes diagnosis. Still, it’s worth carving out a little more space in your memory for something as important as A1C. 

If you’ve recently taken a blood test or if you’ve been discussing or treating diabetes with your doctor, you’ve likely heard about A1C. Only a lab test can accurately measure A1C, and it’s best if a medical professional analyzes it. The results help provide an approximate value for how much glucose has been in your bloodstream on average for the past 2-3 months. Managing A1C effectively will keep you out of your doctor’s office longer, prevent the onset of diabetes and help bring you back from the brink of a diagnosis. In this article, we’ll fill you in on what exactly A1C is and how you can keep an eye on it yourself between blood tests.

What Does A1C Actually Measure?

A1C is not blood glucose (blood sugar). It’s closely related, but not quite the same thing. If you want to explore this more, check out our support page. For now, what you need to know is that blood glucose is the amount of sugar in the blood by weight at the moment you measure it. 

So, what are A1C measurements? They're a representation of the amount of glucose stuck to the hemoglobin in the blood over the months-long lifetime of your blood cells. When bound to sugar, you'd call this hemoglobin A1C, giving us the moniker A1C. The lower it is, the lower your risk of diabetes.

The Difference Between Estimated Average Glucose (EAG) and A1C

Remember, the A1C measurement stems from the two or three months that your red blood cells are alive. So, the test provides your doctor with much-needed visibility into how sugary your blood has been recently. They're able to see this for a more extended period than with CGM and glucometer measurements. But because A1C represents sugar levels over such a long period, your doctor reads the results as an average percentage. This differs from the volumetric measurement of your other glucose readings.

Still, A1C is not a count of your blood sugar: it's the measurement of how much hemoglobin has sugar stuck to it. The blood sugar measurements you’re used to are from the glucose floating around your blood plasma when your meter or CGM takes the reading. So, while A1C can be a helpful tool to estimate how your blood sugar has been on average, it’s not literally your blood sugar count.

You may have had your doctor explain your A1C levels in terms of Estimated Average Glucose, or EAG. Studies have linked EAG and A1C through formulaic conversion. Like A1C, it is an expression of your blood sugar over a few months. It’s convenient for those monitoring their blood sugar since EAG is a more relatable measurement of mg/dL, the same units used on any glucometer or CGM. 

EAG is, as the name implies, an estimated average, and any average is only as good as the data you supply it with. So, keep this in mind when discussing what your measurements may mean for your overall blood sugar outlook. If you're not measuring measure your EAG consistently, it may not give you an accurate representation of your blood sugar. You will get a much more accurate reading if you read your glucose routinely. 

NutriSense recommends regular testing after meals to help provide you and your doctor with consistent information, so that you can get the most benefit from your efforts. Using a CGM can make it easy to keep up the routine, especially when paired with an app and dietitians.

Simple Conversion Formula for A1C From Average Blood Glucose

Now that you know what A1C is and what it measures let's see how to calculate it. You can estimate it using a formula no more complicated than converting Celsius to Fahrenheit (which we admit can be a little hard to remember). All you need to do is apply your average blood glucose measurement to one of the following formulas:

If your blood glucose is in mg/dL (for those living in the US), use this formula:

(46.7 + your glucose) / 28.7 = your A1C

If your blood glucose is in mmol/L (for those living outside the US), use this formula:

(2.59 + your glucose) / 1.59 = your A1C

If you’d like to read more about where these numbers come from, you can check out our source here.

Try Our A1C Calculator

Not everyone loves crunching numbers, so if that formula is too much of a hassle, try our handy estimator:

Remember, you only see a rough estimate when calculating your A1C without using a proper lab test. Any calculator will use your blood glucose to estimate your A1C. As you now know, this is only a derivation and not an actual measurement.

Understanding the Range of A1C

Now that you have an estimate of your A1C, check if you’re at risk for diabetes by comparing your result to the tolerances used by both the ADA and CDC:

The ADA and CDC's A1C Range Tolerances
Normal/Low Risk< 5.7%
Prediabetic/Risky5.7% - 6.4%
Diabetic6.5% >

If your estimated range falls anywhere above 5.7%, get ahead of the risk early. Take control of your health and start monitoring your glucose more closely with a CGM.

Ways to Calculate Your A1C

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

Most CGMs have a feature to provide you with an average of your glucose readings over a chosen period. Using a calculator or formula conversion can help translate those averages into an A1C estimation. Like with EAG, you have to take the data points making up these averages routinely. If they're sporadic or have significant gaps, you could see an unreliable 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. Just keep our previous advice in mind: taking this measurement is an estimation at best.

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 because some insurance plans don’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 current circumstances.

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. Wherever you choose to get them, it’s a good idea to go over the results with a dietitian or doctor who knows your medical history. This way they can discuss potential complications with your unique physiology in mind. Also, remember, since A1C is dependent on the life span of your red blood cells, any related blood disorders affecting you may skew your results. 

Start Optimizing Your Health by Monitoring Your Blood Glucose

However you’re choosing to measure your blood sugar, you can fill in the gaps between tests with on-demand updates with a NutriSense CGM.  Armed with glucose data throughout the day, you can make better-informed decisions and get on track for a healthier life, faster.

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