Sensor & Transmitter Troubleshooting Tips

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Sensor and transmitter troubleshooting tips and FAQ


Find answers to frequently asked questions for your sensor and transmitter.


When and how should I charge the transmitter?
Charge the transmitter each time you change your sensor (which may take up to two hours). To charge, place the transmitter on the charger. When the transmitter is charging, a green light will flash on the charger. When charging is complete, the green light on the charger will stay on, without flashing, for 15 to 20 seconds and then turn off. A fully charged transmitter can be used for a maximum of seven days without recharging.

transmitter inserting into charger

When you remove the transmitter from the charger, a green light should flash on the transmitter. This indicates that it has enough battery power to be connected to the sensor. If you do not see the green flashing light on the transmitter, place it back on the charger until it is fully charged.

transmitter with green light

CAUTION: The transmitter must be charged at least every 60 days. Do not store the transmitter on the charger for more than 60 days. Otherwise, the transmitter battery will be permanently damaged. Disconnect and reconnect to the charger to re-charge again before use.

Your transmitter may look different and that’s okay. The steps to charging the transmitter are the same regardless of the one you use.

When should I calibrate?
After inserting a new sensor, a calibration is needed within 2 hours (after warm-up is complete) and again in 6 hours. After the first day, the minimum calibrations needed is one every 12 hours (twice a day), but you may receive a Calibrate Now alert if one is needed sooner. Calibrating three or four times per day is optimal. It is best to calibrate when your glucose is not changing rapidly. Preferably, before meals and at bedtime.

Is it possible to calibrate too much?
Although calibrating more than 4 times a day will not negatively affect the sensor's accuracy, keep in mind that additional calibrations can lead to calibration errors and unwanted alarms and alerts.

Where can I see how many days I have left on my current sensor?
For your MiniMed™ 670G or 770G pump, from the Home screen, press the center button, select Status, select Sensor and scroll down to see time left on your current sensor.

For your MiniMed™ 630G insulin pump, from the Home screen, press the up arrow to highlight your top status bar. Select Sensor. The sixth icon in from the left looks like a calendar and will have a number in the center. This shows how many days are left on your current sensor. It will also change from green > yellow > red throughout the life of the sensor. Red means it is close to the end of the life of the current sensor.

For your Guardian Connect system, tap on the menu (3 parallel lines) in the top left corner of your app’s Home Screen. You will now see 3 icons in the system status bar. The Sensor Life Icon (calendar icon) will show how many days your sensor has left. The sensor icon will count down with each day that passes.

What does ISIG mean?
ISIG, or the interstitial signal, is the electrical signal that your sensor measures. Your sensor glucose readings are based off your ISIG values.

How do I insert the sensor in the back of my arm?
See how long-time Medtronic customer, Rob, inserts the sensor on the back of his arm.Video icon


What do I do if my transmitter does not flash a green light when connected to the sensor?
If you do not see a green light, follow these steps:

  1. 1. Try to disconnect the transmitter, wait for several seconds and then reconnect. If the green light still does not flash, charge your transmitter.
  2. 2. If that doesn’t work, double check to make sure the sensor is fully inserted into your body, and review the technique on how to insert correctly. Check out the Changing Your Sensor video for steps on how to insert correctly.

Why do I receive 10 pieces of tape and 5 sensors in a product shipment?
Each sensor requires 2 pieces of tape.

Do I need to use 2 pieces of tape for every sensor?
Yes, it’s recommended that you use the 2 pieces of tape included with your sensor. There should be a piece of tape covering the sensor and a piece of tape covering the borders of the transmitter. This ensures that the transmitter doesn’t pull away from the body if it gets caught on something, for example, clothing.

Do I have to use the tape that Medtronic sends?
Different tapes and adhesives are available to hold the transmitter in place and you may need to try different products to find the right one for you. You can review the list of alternate tapes in Tape Tips and Site Management. Or check out tapes available on Diabetes.shop.

Where can I purchase or try out additional adhesive or tape options?
You can purchase adhesives and tapes at www.Diabetes.shop or through the product manufacturer’s website. Here is a full list of product recommendations.

Contact 24-Hour Technical Support at 1-800-646-4633 option 1 for technical assistance or to report product issues. They can also provide a sample kit with various tapes and adhesives.

What do I do if I have skin irritation?

  • Change the sensor and insert it into a different location.
  • Avoid sites where clothes may rub, where your body bends a great deal and your beltline if possible. These areas present a higher risk of the sensor and transmitter being accidentally pulled out.
  • Do not insert the sensor into an area that is lean, scarred, or hardened. If inserted in these areas, it may decrease the flow of interstitial fluid, or the sensor may kink.
  • Try different orientation for the sensor and transmitter. For example, insert so the sensor is on the bottom and the transmitter sits on top. This orientation may help prevent a teeter-totter action at the sensor and transmitter connection which could lead to a lost signal.

Skin sensitives, allergies and skin reactions

Allergies and skin reactions such as itching, rashes or bumps may occur. When you notice them, determine the cause and use a different product. If the site becomes irritated or inflamed, the set or sensor should be removed and inserted in a new location.

Check out our helpful Tape Tips and Site Management.

What do I do if my sensor site bleeds?
Before applying tape, apply pressure to the sensor insertion site until the bleeding has stopped. Once stopped, wipe away the excess blood gently, dry the area, then apply the tape. If there is too much blood, change out your sensor. If bleeding persists, please contact your healthcare provider.

What do I do if my sensors are not lasting 7 days?
Here are some things you can try to help get up to 7 days of wear out of your glucose sensor:

  • Many people have success wearing the sensor on the back of the upper arm. See how long-time Medtronic customer, Rob Howe, inserts the sensor on the back of his arm.
  • Follow our Tape Tips and Site Management. Incorrect taping is one of the most common reasons why CGM sensors won’t stay in place.
  • Try using a liquid adhesive to help your tape stick for longer. Make sure to apply the extra adhesive after you insert your sensor and before you put your tape on.
  • Focus on optimal calibration times. It is best to calibrate your sensor at times when your blood glucose is the most stable. This includes first thing in the morning, before meals, and before bed.

If your sensors are still not lasting the full seven days, request a no-charge sensor replacement.

Call 24-Hour Technical Support at 1-800-646-4633 and select option 1 to troubleshoot further.

What are some of the most common alerts for CGM?
Check out the sensor alerts quick references below for the most common alerts, the reasons they occur and steps to take.


What is the difference between Blood Glucose (BG) required and Calibrate now?

  • A Calibrate now alert occurs when a calibration is needed for your sensor to continue reading. To clear this alert and to continue receiving Sensor Glucose (SG) values, simply enter your current BG and calibrate.
  • A BG required alert occurs when a BG is needed for the SmartGuard™ Auto Mode feature in the MiniMed™ 670G or 770G system to continue running safely. As soon as you enter a new BG, SmartGuard™ Auto Mode will resume (indicated by the blue shield on your home screen).

What does “Sensor updating” on my MiniMed™ insulin pump mean?
Sensor updating is an alert that means the SG (sensor glucose) value is unavailable due to a temporary situation. Don’t calibrate during this time unless notified. This could take up to 3 hours.

Be sure to acknowledge the alert and clear it to avoid a siren. Select OK when prompted on your pump to clear the alert. Follow the instructions on the pump screen. You do not need to change your sensor.

It is important to acknowledge and clear the alert as some sensor updating alerts may escalate to a siren if not cleared in 10 minutes. Before the siren occurs, your pump will beep, vibrate, or both, depending on your audio settings.

At this time, you may be asked to change your sensor. If so, request a sensor replacement.

Tip: Get your sensor lot number ready before you get started. You can find this number on the sensor packaging.

How do I prevent getting CGM alerts at night?
CGM alerts at night may be caused by a few different reasons ranging from sensor insertion to site placement. Here are a few tips to help prevent getting CGM alerts in the middle of the night.

  • Sensor insertion, site placement and taping make a difference. For your sensor to work its best, avoid sites where clothing may rub or constrict, where your body naturally bends which may cause the sensor to pull out and where there is a lot of pressure. See how to insert and tape the sensor properly.
  • Know your calibration status. The calibration icon shows how much time is left until your next scheduled calibration is due and calibrating before bed helps reduce the chance of needing a calibration overnight while sleeping.
  • Customize nighttime alert settings. Talk to your healthcare team about high and low glucose limits overnight to make sure alerts are personalized to meet your needs. You may consider setting both high and low limits differently for the overnight period.
  • Plan ahead. Sleeping in on the weekend? Summer schedule different from the rest of the year? If your schedule changes, think about how your calibration schedule may need to be adjusted to help avoid any unwanted alerts and alarms.
  • Consider the Alert Silence or Mute All Alerts feature.
    • Your pump has a feature called Alert Silence, where you can temporarily silence alerts. Don’t worry, you will still get important low alerts if Alert Silence is ON. For your safety, Low SG (50 mg/dL or below) will always sound, and Alert on Low will sound if it’s turned on. Learn how to set Alert Silence here.
    • Your Guardian™ Connect system has a Mute All Alerts feature where you can temporarily mute all alerts. You can prevent alerts from making any sound by going to Menu > Mute All Alerts to silence all your alerts for up to 4 hours. None of your alerts will make a sound for the entire time that you choose, except for the Urgent Low Sensor Glucose which will vibrate for your safety.

How do I silence my alarms?
When an alarm occurs, something has been detected that is preventing insulin from being delivered. This must be addressed right away. Alarms cannot be silenced.

Your Guardian™ Connect system has a Mute All Alerts feature where you can temporarily mute all alerts. You can prevent alerts from making any sound by going to Menu > Mute All Alerts to silence all your alerts for up to 4 hours. None of your alerts will make a sound for the entire time that you choose, except for the Urgent Low Sensor Glucose which will vibrate for your safety.

screenshot of alerts menu

Your pump has a feature called Alert Silence, where you can temporarily silence alerts. To use the Alert Silence feature, go to the Main Menu > Audio Options > Alert Silence Options. Select All Sensor Alerts or your desired alerts. Select Duration (time) you want and select Begin.

screenshot of audio options

Audio Options menu in the MiniMed™ 670G and 770G pumps. For other products, consult your product user guide.

Why do I keep getting a “Calibration not accepted” alert?
If you receive a “Calibration not accepted” alert, it means that the pump couldn’t update your sensor using the blood glucose (BG) value you entered. This could be because:

  • The BG entered was not within a range the system was anticipating.
  • Your blood glucose levels were rapidly changing.
  • You may have used delayed or incorrect BG entries.
  • It may be an indication the sensor is not working properly.

If you receive a “Calibration not accepted” alert, wait approximately one hour (or until your glucose is stable) to recalibrate. If you receive “Calibration not accepted” a second time, a new sensor will likely be required. If you have recently eaten, exercised, or taken insulin, you might need to wait a little longer than an hour.

How do I upload my CGM data to the CareLink™ system?
If you have a MiniMed™ 770G pump with CGM and are using the MiniMed™ Mobile app, the app is already uploading your CGM data to the CareLink™ system for you as long as your app is always open in the background, and you are logged into the CareLink™ system.

If you are unable to use the phone app, get your free blue USB adapter to upload your device.

Click here for steps to upload your MiniMed™ 770G pump using the blue adapter.

If you’re using a MiniMed™ 630G pump or MiniMed™ 670G pump, you’ll need your Contour® Next link 2.4 meter connected to your pump. The end of the meter is a USB that can be plugged into your computer for downloading CGM data.

Click here for steps to upload your MiniMed™ 630G or MiniMed™ 670G pump.

Your Guardian™ Connect system is already conveniently linked to your CareLink™ Personal account. To view reports on your computer, go to www.carelink.minimed.com to login to your CareLink™ account using your username and password you created. From there, you will be able to generate reports with your data for you and your provider to review.

How do I get a replacement sensor?
To request a sensor replacement, click here.

Tip: Get your sensor lot number ready before you begin the process. You can find this number on the sensor packaging.


I am still experiencing issues with my transmitter after troubleshooting. What can I do?
If you are still experiencing issues, you can request a replacement.


Need more product support?

If you’re still having issues with your continuous glucose monitor and would like additional help, call our 24 Hour Technical Support Team at 1-800-646-4633 and select option 1 or send us a message.