Troubleshooting 101 for Continuous Glucose Monitors


Continuous glucose monitors (CGMs) are small wearable devices that have helped people better manage their diabetes. They consist of a small sensor that stays in your skin and a transmitter that sits on the surface of your skin. Not having to prick your finger is one of the many benefits of using a CGM.

There are now several different brands of CGM on the market, including Abbott’s FreeStyle Libre 3, Dexcom’s G7, Medtronic’s Guardian Connect and Senseonics’ Eversense system.

Since they are still fairly new medical devices many insurances may not cover all CGMs. However, some insurances like medicare and TRICARE have made changes to their coverage policy to make CGMs more easily accessible.

But getting a prescription for a CGM is not the only hurdle you may face. Once you have a CGM, there may be some troubleshooting that you’ll have to do while you get used to wearing it and to ensure your tech is working properly.

Here are some common errors that happen when you wear a CGM and how to troubleshoot them.

Botched Application of Sensor

Each CGM comes with specific instructions on how to apply your sensor, but there may be times where the applicator doesn’t work properly. Maybe the spring sprung before you pressed the button or the applicator didn’t release the sensor after you ejected. Don’t throw it away. Here is what you can do if any of these happen.

  • Don’t try to reapply or reinsert the sensor.
  • Save the sensor and any packaging it came in. Manufacturers may need sensor and/or transmitter information.
  • Call the manufacturer to have them send you a free replacement. Here are the customer contact info for the CGMs available:
  • Send back the broken sensor if they ask for it

Your Sensor Falls Off

If you are new to wearing a CGM, it may feel awkward at first and you may bump it several times. Depending on where on your body you wear your sensor, you may accidentally knock it off during exercise, while taking off your sports bra, or it may immediately fall off after application. Here are some tips to help avoid knocking off your sensor.

  • Make sure you clean the area with an alcohol wipe before application.
  • Avoid having any lotions on before application.
  • Use a liquid adhesive before application to help keep the sensor on.
  • Try a different application site that you’re less likely to knock off. Confirm that the site is usable with your healthcare provider first.
  • Do not exercise or shower immediately after application to avoid letting any sweat or water get into the sticky adhesion.
  • Use a patch over your sensor. There are many available online for purchase, but some manufacturers like Dexcom provide patches for free.
  • If your sensor does fall off, contact the manufacturer for a replacement.

Losing Signal With Your Phone

Most CGMs come with mobile apps that allow you to use your phone as a monitor instead of the one that comes with your sensor. However, there may be times where you get alerts indicating that your phone has lost signal to your sensor. This may not be an issue with your sensor, but rather your phone or the mobile app. Here are some tips for possibly fixing this error.

  • Make sure your phone is within range to receive signals or that there is no water in your sensor.
  • Since your phone receives signals via bluetooth connection, try turning your bluetooth setting on your phone off and back on manually.
  • Make sure there is no pressure being applied to your sensor. This can happen at night if you sleep on it.
  • Keep your phone charged. Low power mode will turn off bluetooth settings and may interfere with receiving signals from your sensor.

Skin Reaction to CGM Adhesive

CGMs adhere to your skin with an adhesive, a sticky backing that bonds with your skin. Several studies have shown that people have an adverse reaction to the adhesion used in some CGMs. Because not all CGMs are manufactured the same, you can always request a different CGM from your healthcare provider if you are developing skin rashes to the adhesive. Here are some tips if this happens to you.

  • Make sure to rotate CGM sites. Using the same site can lead to more skin irritation with repeated use over time.
  • Ask your doctor for patch testing. Patch testing exposes your skin to several adhesives to see what your body may react to.
  • Use an adhesive remover when taking off your expired sensor.
  • Apply a liquid adhesive or patch underneath your sensor.

Wearing a CGM can have a learning curve, but once you’ve mastered how to apply it and keep it on, it can really help improve your diabetes management.

Educational content related to continuous glucose monitor technology is made possible with support from ​Abbott, the makers of the Freestyle Libre 2, an active partner of Beyond Type 1 at the time of publication. ​Editorial control rests solely on Beyond Type 1.

WRITTEN BY Liz Cambron-Kopco, POSTED 03/22/22, UPDATED 03/29/23

Liz has been living with type 2 diabetes since 2014, but grew up surrounded by it as a first-generation Mexican-American. With a bug for research, Liz pursued a PhD in molecular biology and spent her early career studying insulin signalling in invertebrates to understand how insects' tiny little bodies work. Along with advocating for women and girls in STEM, Liz shares her personal journey with diabetes on her social media platforms to help teach people to become their own advocates. Her passion for advocacy led her to join the Beyond Type 1 team. When she's not advocating, Liz enjoys hiking with her husband and their terrier/schnauzer mixed pup Burberry.