Dexcom G5 Error 121- [Reasons and Ways To Fix]

The Dexcom G5 is a Continuous Glucose Monitoring (CGM) System that provides real-time glucose readings. The device tells their sugar levels after every five minutes. There is more. 

Dexcom G5 Mobile can easily access and share dynamic glucose data anywhere, anytime to your device. But sometimes, it shows error 121, stopping you from using the machine.

So, what is Dexcom G5 Error 121?

Dexcom G5 Error 121 is related to a software bug, according to the manufacturers. If you shut down the device or use a different charger, the error message may show up. The message also comes with alert noises that annoy the users most. However, fixing the issue is not that complicated.

The causes and the fixes are discussed here in detail. Follow the recommendations here and keep using Dexcom for a longer period.

What Is Dexcom G5 Error 121?

Dexcom G5 Error 121 is commonly found in the Dexcom G5 CGM System. If you visit user forums, the intensity of the error code will bother you a lot.

Similar to the error code in true metrix, you will find numerous guesses and predictions. However, there might be two reasons behind it.

Receiver Shut Down

Mostly, this error occurs if you shut down the receiver (display device). The correct way is to halt it and not shut it down completely. If you have the user manual, it says many times not to turn off the device. Instead, it’s better to wait.

The waiting time sometimes exceeds 10 minutes and at that time it’s better to call customer care. Dexcom has excellent after-sales service and they will offer you on-time services.

Charger Issues 

Sometimes, you may get Dexcom G5 Error after using another charger. 

Some users confirmed that CGM Systems got Error 121 as they shut down the Dexcom receiver. But this happens when it is on charging. When the users did this, the sensor stopped too. 

After charging was complete, they powered on the receiver, and it was showing error 121. So, it’s been very clear that NEVER shut down the sensor. Just stop it if you have to charge the Dexcom receiver device. 

How To Solve Dexcom G5 Error 121?

You can resolve the Dexcom G5 errors via multiple techniques. You may fix the hardware error by yourself by following the Dexcom G5 user manual instructions. However, contact the Technical Support Team if there’s a technical error or software bug.

By Replacing The Receiver

ERR121 is a common software bug that can only be fixed by replacing your Dexcom receiver. The representatives recommended not to use the SHUTDOWN option of the receiver.

Dexcom G5 Troubleshooting

Choosing Troubleshooting to resolve the error 121 can also solve the problem. Although it doesn’t work for everybody, still there is no harm in trying. 

Other Common G5 Errors

In addition to Error 121, you can get other error messages on your CGM too. These are discussed here. 

No Alarm/ Alerts 

When the sensor, receiver, and transmitter are faulty, the device won’t play alarm or alerts. So, when you have low or high sugar levels, you will not know. This could be a simple setting error. To resolve this issue, check your mobile app or smart device. Silent or Do Not Disturb mode should not be on.

False Sensor Glucose Reading

BG Meter, Display Device, or Receiver show false readings due to error. You must calibrate the device to resolve the issue. Just wait for further prompts. Sometimes, the CGM System will resolve this error by itself. However, if it lasts for hours, you should contact the Technical Support Team.

Hardware Errors

Hardware error occurs in the receiver of the CGM system. Generally, the reasons behind this are dead or low battery and auto turn off the device. But sometimes, the reasons can be a corrupted database and Bluetooth connection error on the smart device. 

Follow the safety instructions to resolve these errors. Only charge the receiver with electrical power. You can also reset the device or contact the support team.

Calibration Error

BG meter fails to calibrate if the reading range is 40-400mg/dL. Sometimes, the issue might be with the smart device app. It doesn’t accept and display the sensor glucose reading until the issue is settled. 

To resolve the calibration error, you should first wait for 15 minutes. Then, calibrate the system and wait for resetting. However, if the issue persists, call the Technical Support Team.

Transmitter Error 

Due to transmitting errors, the transmitter and receiver device won’t work properly. Moreover, the sensor session will be stopped, and the glucose readings will not be displayed. You must contact the support team, reset the alert/ alarm system, or order a new transmitter.

Wondering How to change the Dexcom G5 transmitter?

Unpack the transmitter, and follow the instructions carefully to apply the new transmitter. Connect the transmitter to the sensor and display device to check the readings. 

If Nothing Works: Contact Dexcom 

Dexcom customer service is top-notch. If the issue is not resolved by you, contact the Dexcom teams.

Contacting Technical Support 

The technical support team helps you to fix Dexcom G5 errors. You can get replacement units and guidelines about technical as well as software-related issues from them. 

Users can contact the technical support team through Email or by Phone.


Phone: 1-888-738-3646

Contacting Dexcom Patient Care Team

This is a certified team offering the users customer care and tutorial services regarding the CGM. You may learn initial CGM system training, product care, and error fixation.


Phone: 1-858-200-0200

So, that’s How to fix Dexcom G5 Errors. 

Moreover, you should take care of the device to avoid any errors in the future.  

How to Take Care of Dexcom G5?

Dexcom G5 maintenance is relatively simple due to the simplest built-in features of the system. Learn the basic maintenance of your Dexcom G5 system. You may also read these instructions from the manual book of the CGM System.

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  • You should not open the package until you’re ready to use it.
  • The G5 transmitter is reusable but only by the same person who first put it.
  • When the sensor and transmitter are not in use, pack them for later use.
  • Be mindful that the receiver (display device) is just splash resistant. Therefore, it must be kept in a dry spot.
  • Your receiver device must be properly charged & unplug instantly as it is fully charged.
  • Prevent sensor, transmitter, receiver, and USB port from the fluid.
  • Reset the receiver’s battery whenever the system delivers the alert.
  • Plug the micro USB cable into the transmitter device for charging. Avoid plugging the cable into the Laptop or PC.
  • Close the USB port door after unplugging the cable to keep it clean and arid.

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Why A Continuous Glucose Monitoring (CGM)Is Helpful?

You need to keep a check on your Glucose, and that’s what CGM does. Dexcom G5 provides you with the world’s fastest CGM System on your compatible device. It allows you to view and share your glucose data with your loved ones. 

You can use fingersticks to test your sugar level. In addition, this system also tells in which direction your sugar level is going. You can measure your blood sugar any time from day to night. Plus, it will also show you where it should be! 

You can also make your diet plan by observing the readings and graphs. You can decide about eating carbs and proteins or stop the current dietary supplements. You can discard any meals or drinks containing sugar and caffeine after observing the readings. 

You can try different protein shakes that are healthy to maintain your sugar level. 

Let me tell you another useful feature of Dexcom G5. You can use your smartwatch as a display device to see your glucose data. This system provides you with the facility to track your glucose levels at your home. So, know the readings and then decide whether a scoop before a workout is worth it. 

CGM System Components

The CGM System consists of three main components. These are a small sensor, a transmitter to convey the data, and a display device.

Small Sensor: It is inserted just beneath your skin. This enables the device to easily measure the glucose level in your blood.

Transmitter: It is designed to deliver the glucose data of your body to a display device. This can either be a smart device or a receiver connected wirelessly.

Display Device: It receives glucose data transmitted by a transmitter. The display device can be either a Dexcom G5 mobile app or a receiver. You can only use one display device at a time (throughout the session) 


What is the difference between Dexcom G5 and G6?

For G5, the transmitter is coded while the sensor is not. However, for G6, both the transmitter and sensor are uniquely coded for accurate readings. 

Moreover, for Dexcom G5, calibration is necessary. However, for G6, it’s up to you whether to calibrate it or not. 

Is G5 better than G6?

Dexcom G6 is better for an accurate glucose reading. G5 also has an auto insertion feature for the sensor. G6 also doesn’t require any fingerstick calibration of the system. The Dexcom G6 CGM system is faster than the G5 system. 

What are the basic Dexcom G5 Errors?

No display of glucose reading, disconnection of the Bluetooth, software bugs are common errors. However, you may also face auto shut down of the transmitter/ sensor, hardware, and calibration errors.

Final Words 

I hope you have understood the Dexcom G5 Error 121 and related information. Getting 121 errors is common, there is no need to worry.

It happens due to receiver shutdown and charger issues. But the great news is you can solve the problem. You can replace the receiver, do troubleshooting, and contact Dexcom teams to solve this error. 

Dexcom G5 is indeed a great device that every diabetic should have. If you are one of them, keep on using it and stay healthy!

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