How Does a Continuous Glucose Monitor Work?

Implantable glucose sensors

Right now, EVS is the only implantable glucose sensor available. It includes a fluorescence-based sensor, an external transmitter, and a mobile app to display glucose data. A medical team puts the sensor into your upper arm, then the transmitter on the skin over it to collect data and send it via Bluetooth to the app on your phone.

This system needs a 24-hour warm-up and a 12-hour sensor calibration period several times. You have to charge your transmitter for about 15 minutes every day.

Sensor-augmented pumps

If you use an insulin pump, you can also link it to your CGM system for continuous care. You won’t need to manually program the pump as with the other finger-prick methods. This is called a “sensor-augmented pump.”

Sensor-augmented insulin pumps are a better choice because they offer advanced features such as automatic basal rate adjustments and predictive glucose management. These features improve blood sugar control and lower hypoglycemia, especially during challenging activities. They combine data from CGMs directly into the pump, making it easier for people with diabetes to manage their condition in real time. These systems require detailed training and support from specialists to make sure you use them correctly.

Why Use a CGM?

Unlike traditional glucose meters, CGM records your blood sugar levels throughout the entire day and night, showing your highs and lows over the entire week. The systems can help:

• Record dangerously low overnight blood sugar levels, which often go undetected
• Track high levels between meals
• Show early morning spikes in blood sugar
• Assess how diet and exercise affect you
• Figure out if your treatment plan works on a day-to-day basis

CGM isn't right for every person with diabetes, though. They’re more expensive than glucose meters, and your insurance or Medicaid might not cover one unless you take insulin medication. You may also need some extra training and practice to use the technology correctly. Also, CGMs don't completely get rid of the need for finger-prick checks, but they do lessen how often you need to use them. It's important to talk to your diabetes health care provider about when and how often to check your blood sugar with finger pricks.
 

Short-Term Continuous Glucose Monitoring

Researchers have been trying to figure out whether short-term continuous glucose monitoring (CGM) can improve blood sugar control and behavior. 

One study assessed a 10-day trial of CGM in kids and young adults with type 2 diabetes. While short-term use of CGM didn't significantly improve blood sugar levels, it did lead to positive behavior changes. Participants checked their blood sugar and took insulin more often. They also expressed a desire to continue using CGM long-term. Future studies may better clarify the impact of short-term CGM use on blood sugar control.

Who Can Use Continuous Glucose Monitors?

Your doctor may suggest a CGM if you have:

• Major highs and lows in your blood sugar levels for no clear reason
• Gestational diabetes, which happens during pregnancy
• An insulin pump
• Blood sugar levels that are very low, called hypoglycemia, or very high, called hyperglycemia

Adults and children aged 2 and older can use the device. The FDA recently approved smartphone apps to pair with the CGM. Information on blood glucose is shared immediately. It’s expected to be a great help to parents and caregivers who can’t always be in the same place as the person who has diabetes.

Tips and Tricks for Continuous Glucose Monitors

Here are some tips for using your CGM:

Take calibration seriously. Always wash your hands before taking a fingerstick for calibration. If you can't wash, use the second drop of blood after wiping away the first drop to avoid incorrect readings caused by dirty hands.

Retake fingerstick. If your CGM and fingerstick readings are far apart, wash your hands and retake the fingerstick to make sure the CGM or meter is accurate. This can prevent insulin overdoses.

Calibrate when glucose is stable. Avoid calibrating when your blood sugar is low or changing quickly. Mornings or before bed are good times to calibrate since glucose is often stable.

Be cautious on day 1. CGMs can be less accurate on the first day, especially right after inserting a new sensor. Be patient and understand accuracy tends to improve over time.

Improve day 1 accuracy. Try inserting a new sensor several hours before activating it while the old one is still running. This will allow for a better warm-up and improved accuracy on the first day.

Switch devices if needed. Try different brands if your CGM and blood glucose meter don't match well. The accuracy of both devices can vary depending on the brand and model.

Alarms are helpful tools. View CGM alarms as valuable tools for tracking your glucose, not something negative. Adjust the alarm thresholds to what feels best for you.

Avoid over-correcting highs. Avoid overreacting to high glucose alarms with too much insulin.

Pay attention to trend arrows. Use the arrows on your CGM to guide insulin adjustments. Rising arrows may mean you need more insulin, while falling arrows may mean you need less.

Try different sensor wear locations. Consider trying different skin locations, such as the back of your arm or abdomen, to find the best spot for accuracy.

Watch out for Tylenol. If your CGM device reacts to acetaminophen (Tylenol), avoid relying on sensor readings for several hours after taking it.

Risks of Using Continuous Glucose Monitors

Possible drawbacks of using CGMs include:

• Information overload. Too much information from your CGM can lead to stress, burnout, and unhealthy eating habits.
• Alarm fatigue. Too many alarms can cause distress and disturb your sleep.
• Skin irritation
• The constant presence of a sensor in or on your body might be uncomfortable.

The Future of CGM

The FDA has approved the first over-the-counter CGM, the Dexcom Stelo Glucose Biosensor System. This device is for people aged 18 or older who don't use insulin. It is meant for people who manage their diabetes with oral drugs or those without diabetes who want to track how diet and exercise affect their blood sugar.

It's not suitable for people with dangerously low blood sugar (hypoglycemia) since it doesn't alert users to this condition. The Stelo system uses a wearable sensor that connects to a smartphone app, providing blood sugar readings every 15 minutes. You can wear each sensor for up to 15 days. But you should talk to your doctor before making medical decisions based on the device's data.

Scientists are also testing new and better CGM systems in clinical trials. The technology is also a key part of researchers’ efforts to build an artificial pancreas that could mimic the body’s natural process of controlling insulin.

Takeaways

Continuous glucose monitors (CGMs) track blood sugar levels around the clock, providing valuable data for managing diabetes. They measure glucose through a sensor placed under the skin, which sends readings to a monitor or smartphone. CGMs help identify trends, reduce hypoglycemia, and guide insulin adjustments, making them beneficial for diabetes management. 

However, CGMs require regular calibration, can be costly, and may cause information overload or skin irritation. New advancements, including over-the-counter CGMs, are making the technology more accessible, and ongoing research aims to improve accuracy.

Continuous Glucose Monitors FAQs

What is a blood glucose monitor watch?

Blood glucose monitors are smartwatches that claim to measure blood glucose levels without piercing your skin. The FDA has not approved them and warns people not to buy or use them.