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Dexcom G6 Troubleshooting Guide

Dexcom G6 Troubleshooting

Your Dexcom G6 continuous glucose monitor (CGM) makes managing type 2 diabetes easier by incorporating the latest technology so you can see your glucose numbers in real-time.
People sometimes report issues when they first use a CGM and we’ve compiled some of the most common problems and solutions below:

Dexcom G6 Signal Loss or Poor Signal

If you’re experiencing signal loss or poor signal strength, first check that your phone’s Bluetooth is turned on. Try turning your Bluetooth off, then back on, then wait 10 minutes.

If your signal does not reset, try any of the following tips:

Ensure the phone’s Bluetooth is paired with the Dexcom transmitter. Under phone settings, check that your Dexcom transmitter appears in the list of paired devices.  If it does not, first delete all of the paired devices from the phone.  Go to the Dexcom app settings, delete then re-enter the transmitter serial number and repeat the transmitter pairing process.
Restart the smart device and reopen the Dexcom app. Close all background apps before following this step.
Make sure your smart device is charging/charged. Low power mode will turn off Bluetooth on some smartphones.
Always keep your phone within 20 feet of the sensor. The transmitter holds 10 minutes of glucose data.  After 10 minutes, data points will be dropped and there will be gaps in the CGM trend graph.  In general, this means the phone needs to be in the same room as you.
Make sure the signal is not blocked. Bluetooth is unable to transmit through or around water, cement or steel walls or other dense barriers.
Keep the phone on the same side of your body as the sensor. The sensor signal can be blocked by body tissue because the body is mostly water. For example –– If the sensor is on the side of an abdomen that protrudes, the signal may not be able to reach a phone kept in a pocket on the opposite side of the body.
Remove old transmitter info from Bluetooth list and try again. If you are experiencing difficulties connecting a new transmitter to the device, try to remove old transmitters from your Bluetooth list.
As a final note, always clean the back of the transmitter with an alcohol wipe each time before attaching it to a new sensor.

Sensor Not Found or Sensor Loss

If your sensor’s signal is lost, wait at least 15 minutes after ending a sensor session before trying to start a new session.
Check to see if the correct transmitter serial number has been entered in the app. The transmitter serial number is found on the back of the new transmitter and on the transmitter box.  A new serial number must be entered in the app each time the transmitter is replaced.
Dropped glucose data points are the first sign that a sensor may be failing prematurely. Some sensors can have faulty manufacturing.  A sensor that stops giving readings before the 10-day session is completed and transmitters that stop sending glucose data to the app prior to the 90-day expiration may be returned to Dexcom for replacement. Contact Dexcom Customer Support at 1 (888) 738-3646.
Note: Always store sensors in a dry place where the temperature remains between 36-86 degrees F.

Sensor Detaches Before the 10-Day Session Has Ended

If your sensor detaches, be sure to remove all paper backing before inserting the sensor. Hold inserter firmly against the skin for 30-60 seconds before pressing the inserter button. Immediately after insertion, rub firmly three times over the entire patch and smooth out any wrinkles.

Good skin preparation is very important for the sensor to adhere well:

  • Your sensor site should be flat, clean, and completely dry before you insert the sensor.
  • Scrub the site thoroughly with an alcohol wipe and let dry.
  • Apply sensor patch to an area with as little hair as possible.
  • Shave hair on the area where the sensor is to be applied if needed.

Don’t forget to change to a new site with every sensor session.

Remove any residue from past sensors with alcohol wipes or with an adhesive remover such as Unisolve, Detachol or Tac Away. It may take time for the patch to fully dry and stick since skin types vary. During that time, keep your skin dry and avoid engaging in activities that may make you sweat.
If you insert a new sensor before bed, ensure the warmup period is complete before going to sleep.

Always apply the sensor to an appropriate body area:

  • The Dexcom sensor has only been tested for accuracy in the abdomen.
  • The Dexcom sensor is not intended to be worn on the back of the arm. The sensor may not read accurately or stay attached in this area.
  • Avoid placing the sensor patch where the skin folds when you bend.
  • Avoid placing the sensor underneath a waistband.

As a rule of thumb, apply the sensor where at least ½”-1” of fat (not skin) can be pinched between thumb and forefinger.
When using adhesive supplements placed under or over the sensor patch, avoid the spot where the needle inserts. Be sure to let it dry.

Commonly used adhesives:

  • Skin-Tac wipes or solution – may also daub or wipe solution under any loose section of the skirt. Note that the product becomes stickier as it dries.
  • Mastisol solution – same as above.
  • Dexcom overpatch – this is a clear plastic cover shaped to be placed over the sensor which helps hold loosened fabric skirting onto the skin. The overpatch is effective for securing the sensor when swimming, both in chlorinated and saltwater.  You can order free overpatches at

Skin Reactions

Applying a barrier for protection underneath the sensor patch can help prevent redness, itching and skin eruptions or erosions due to adhesive sensitivity.
A chart showing benefits and professional tips for various adhesive supplements, adhesives, tapes and protective barriers can be found at:
Consider joining a user group such as the Facebook Group: “Dexcom and Libre Rash” to explore ideas and suggestions that have worked for other Dexcom users experiencing skin reactions.

Readings Not Matching Blood Glucose (BG) Meter

It’s first important to understand that blood glucose (BG) meter readings will never exactly match the sensor reading. The degree of error in the Dexcom G6 CGM system (9.5%) is equal to the most accurate meters available today (10%). Older and off-brand meters may have considerably lower accuracy than the G6 system.

Expect a lag time.

First, your sensor readings may not match your finger stick readings during the first 24 hours of use. Be sure to use finger sticks during this period if your readings don’t match how you feel.
Second, general lag time is normal. This is a normal system function for the current state of all CGM technology. Since CGM sensors are not measuring BG directly, but rather the fluid surrounding fat cells below the skin, it takes some time for glucose to travel from the blood into this space.
When BG is changing rapidly, it takes some extra time for this change to show up on the sensor. The lag time is greater when BG is falling.
The CGM reports a BG value every 5 minutes. It reports the average of readings over the past 5 minutes.  The data being displayed may be anywhere from 2.5 to 7.5 minutes.
Total lag time for all factors is estimated to range from 6-12 minutes. When BG is rising, the CGM is likely to display values that are LOWER than the actual BG. When it is falling, the CGM is likely to display values that are HIGHER than the BG.

Calibration is not necessary with Dexcom G6

Calibration is sometimes done by individuals when they believe their CGM is not lining up well with their blood glucose readings in their finger sticks. The Dexcom G6, however, self-calibrates all on its own during the first 24 hours of wear making calibration completely unnecessary.
Calibration with the Dexcom G6 CGM system is not necessary:

  • The Dexcom G6 CGM System stands out as the first real-time, integrated CGM (iCGM)that does not require finger sticks or calibrations to give accurate readings. As long as you enter the unique Dexcom G6 sensor code that is printed on each sensor’s adhesive label during the startup period, no calibrations are required.
  • During the first 24 hours of a newly inserted Dexcom G6 sensor is when it is self-calibrating which means during this time frame sometimes the glucose readings will be less consistent with those of a blood glucose meter. Those readings become more aligned as the sensor becomes more accustomed to your body over the first 24 hours of sensor use. If you are concerned during the first 24 hours of wear, finger sticking is always an option.

If you are still concerned with your CGM’s accuracy you can double check it using the 20 rule. Your Dexcom G6 device should be within:

  • 20% of the meter value (blood glucose meter) when the meter value is 80 mg/dL or higher
  • 20 mg/dL of the meter value (blood glucose meter) when the meter value is under 80 mg/dL

If your sensor readings are in fact not lining up, contact Dexcom Customer Support, 1 (888) 738-3646, for replacement of a sensor that is not operating within this manufacturer specification. They will help get you a replacement device.

Ensure proper calibration, if needed.

The Dexcom G6 CGM does not require any calibration when the sensor session is started using the code, unique to each sensor. The code is printed on the paper covering the sensor adhesive.
If starting a sensor without the code, the sensor will require 2 calibrations per day, 12 hours apart. Lag time and calibrations are the most crucial teaching concepts for successful real-time CGM use, particularly to users over 55 years old.
Principles for proper G6 calibration include:

  • Perform a high-quality BG check: Wash hands with soap and dry thoroughly. Use a fresh lancet.
  • Check BG from a fingertip, not an alternate site.
  • Do not wipe the finger with alcohol before puncture.
  • Check that test strips are not expired and are stored according to instructions on the container.

Use a reliable meter with high accuracy.

If the meter is more than 2 years old, consider replacing the meter.

  • Do not calibrate more frequently than twice per day for a “no code” session, or once in the initial 24-hour period of a “code” session.
  • Do not calibrate unless the CGM trend arrow is horizontal. BG values are generally more stable before meals.  Avoid calibrating right after meals.
  • Do not calibrate during recovery from hypoglycemia.

Pressure Effect and Compression “Lows”

Pressure on the sensor can cause falsely low glucose readings. Since the G6 sensor filament is resting in tissue surrounded by fluid, and measuring the glucose concentration in this fluid, pressure on the sensor pushes glucose away from the sensor.
When the pressure is removed, the G6 sensor reading usually returns to the same glucose level it was at before the pressure occurred.
Remember, what works best for one person may not work well for everyone. You may need to try several different methods to figure out what works best.