The content in this article should not be taken as medical advice. Please consult with your healthcare provider regarding your individual health needs.
Picture this: Your friend made her famous red velvet cake for your birthday and she’s so excited for you to try it. Though you’re focusing on your glucose health, you want to celebrate with your friend and enjoy the moment—it is your birthday after all. You enjoy the delicious cake, and afterward, you check in on your glucose.
Your Stelo biosensor level is 117 mg/dL with an up arrow, but you feel like your glucose levels might be a little higher than that given the piece of cake you just ate, so you decide to check with a fingerstick. Your blood glucose meter (BGM) reads 139 mg/dL. Why are these numbers different and what is accurate? Like many things in life, the answer is not so cut and dry. Let’s take a look into what accuracy means when it comes to measuring your glucose so you can feel confident in knowing your levels.
How accurate is Stelo?
We can all agree that accuracy is important when it comes to tracking your glucose; you need to know how that red velvet cake actually affected your glucose so you can course correct if necessary, perhaps by taking a 10–15-minute walk. That’s where Stelo can help—the most accurate biosensor1 available made by Dexcom, a leader in glucose tracking with 25+ years of experience developing industry-leading technology.
Dexcom follows rigorous testing protocols to ensure the accuracy of their glucose biosensors and continuous glucose monitoring (CGM) systems. Here are some key aspects of the testing process for Stelo:
1. Clinical trials
Dexcom conducts extensive clinical trials where the performance of its biosensors is compared against "gold standard" laboratory methods. These trials involve directly measuring glucose concentrations in the blood using advanced laboratory equipment.
2. Large-scale testing
In one of our studies, Dexcom analyzed 20,000 laboratory tests and 20,000 Stelo biosensor readings simultaneously.2 This large sample size helps ensure the robustness of their findings.
3. Accuracy comparison
The accuracy of Dexcom devices is benchmarked against the YSI (Yellow Springs Instruments) Analyzer, which is considered one of the most accurate methods for testing blood glucose levels. In these tests, the Stelo biosensor, which measures glucose in the interstitial fluid, was found to be 93% accurate compared to this gold standard.*,1
4. Continuous improvement
Dexcom continuously updates their testing protocols and standards to incorporate the latest scientific advancements and regulatory requirements. This ensures that Dexcom biosensors remain at the forefront of accuracy and reliability in glucose monitoring.
Understanding the accuracy of Stelo
We’ve established Stelo is 93% accurate,*,1—but what does that really mean? It means that 93% of Stelo readings fall within 20/20% YSI (Yellow Springs Instrument) test criteria. This gold standard method is considered to be the most accurate way to test glucose.
The 20/20% YSI criterion for accuracy states that:
- If a lab result is greater than 70 mg/dL, the Stelo value must be no more than 20% higher or lower than the reference value.
- If the lab result is less than 70 mg/dL, the Stelo value must be within 20 mg/dL of the reference value.
For example, if a lab measures a glucose value of 100 mg/dL, any Stelo reading between 80 and 120 mg/dL is considered accurate.
It's important to note that all glucose biosensors and CGM systems, including the Stelo Glucose Biosensor, have specific accuracy ranges. Additionally, comparing Stelo to blood glucose meters may not be helpful because each has a different margin of error.
Pro tip for Stelo users: Landscape mode
The Stelo biosensor updates your glucose readings every 15 minutes. So, if you’re looking at a reading from 14 minutes ago and your glucose is changing, that number might feel inaccurate. And, at times, your glucose can change rapidly in 15 minutes.
To get a bigger, more fluid picture of your glucose trends, turn your phone sideways and view your Stelo app in landscape mode. This helps to put the changes in perspective as you have a less consolidated view of the graph.
Digging into the difference: Biosensor vs. BGM
The first difference to understand is that Stelo measures glucose in the interstitial fluid that sits just below your skin, while a BGM measures glucose in a drop of blood, usually from your finger. Not only do Stelo and BGMs have their own margins of error, but each different brand of BGM differs from one another—and some are better than others.
There are other reasons why you might be seeing a large discrepancy between your Stelo and BGM2—here are a few.
- Rapidly changing glucose: When your glucose is rapidly changing, it can be more difficult to compare your BGM value and biosensor reading because your blood glucose will change before the glucose in your interstitial fluid does. The numbers should be closer when your glucose stabilizes.
- Hand cleanliness: For example, if you’ve just been snacking on some fruit, you could have residual sugars on your fingers that will affect your BGM reading. Make sure to wash your hands with soap and water (not hand sanitizer) then dry them before a fingerstick. Many inaccurate BG meter values are from hands not being washed thoroughly before testing. When using test strips, make sure they’re stored as directed and not expired.
- You’re wearing a newly inserted Stelo biosensor: Accuracy in the first day may vary due to your body's immune response from inserting the sensor—each person’s reaction is different.
- Pressure on the sensor: If you’ve been laying or leaning on your biosensor, it can cause falsely low readings. When you relieve the pressure, the numbers should become more accurate.
Confidence driven by accuracy
From hitting a bullseye in archery to getting GPS directions in an unfamiliar city, accuracy is crucial. Whether you’re trying to determine if your glucose can handle that piece of red velvet cake, or you’re looking to improve your overall health and wellness, Stelo is there to help.
Stelo takes accuracy very seriously, and is built on technology from Dexcom, a leader in CGM technology for decades. More than 20 years ago, the first CGM system from Dexcom was introduced in the US. And in 2018, Dexcom became the first FDA cleared CGM system designed to replace fingersticks† for people with diabetes, thanks to its reliable accuracy and performance.
You can rest assured that in order to replace the routine use of fingersticks,† Dexcom CGM systems and the Stelo Glucose Biosensor must meet rigorous accuracy benchmarks when compared to laboratory standards. That’s accuracy you can be confident in.
Curated & reviewed by: Kristyn Milburn
MSN, NP-C, BC-ADM, CDCES
MSN, NP-C, BC-ADM, CDCES
Kristyn Milburn is a dedicated nurse practitioner and diabetes care and education specialist, holding board certification in advanced diabetes management.
Written by: Stelo Team
*Percent of iCGM values within 20% of comparator glucose. †Fingersticks required for diabetes treatment decisions if symptoms or expectations do not match readings.
1 Dexcom, Data on file. 2024.
2 Stelo User Guide.