Continuous Glucose Monitoring CGMS
A continuous glucose monitoring system (CGMS) is an FDA-approved device that records blood sugar levels throughout the day and night.
There are several approved devices -- Medtronic iPro device, DexCom G4, G5, or G6 device, and the Abbot Libre systems, for example (details below) -- that can provide up to many blood sugar measurements continuously. The doctors at Houston Thyroid and Endocrine use this technology to help manage a patient's blood sugars.
How is it placed?
First, a tiny glucose-sensing device called a "sensor" is inserted just under the skin of the abdomen. The insertion is quick, and is usually not painful. Tape is used to hold it in place.
The sensor measures the level of glucose (painlessly) in the tissue every 5 minutes and sends the information via a wire to a cell phone-sized device monitor that you attach to a belt or a wireless device in your purse/pocket. The system automatically records an average glucose value every five minutes for up to seven days.
When is this used?
The continuous glucose monitor is now intended for day-to-day monitoring or long-term self-care, and it is a replacement or equivalent to standard blood sugar monitoring. It gives trends. This helps your health care team make the most appropriate decisions regarding your diabetes treatment plan.
Here are video tutorials:
Is It Accurate?
NO and neither is your glucometer. But it is precise.
The gold standard blood sugar is obtained from whole blood at a laboratory from your arm and this would be the most ACCURATE blood sugar. Within a range of 80-150 all glucose meters and CGM (Dexcom, Libre, Enlite, Eversense) are approximately plus or minus 15% versus whole blood. The same applies to any blood glucose meter as well. Therefore, a blood sugar meter and a continuous glucose monitor could potentially be up to 30% different from each other. Both devices however are PRECISE within their own measurements and can be used for trends. This difference worsens with more extreme lower or higher blood sugars. Example image to explain accuracy versus precision is here:
https://www.researchgate.net/figure/Illustration-of-accuracy-versus-precision_fig1_242016279
Comparisons Between Libre and Dexcom:
**********PLEASE BE AWARE IF YOU OBTAIN A CGM AND YOU WOULD LIKE FOR US TO HELP YOU PUT IT ON, PLEASE CALL THE OFFICE 713-795-0770 OR SEND PORTAL MESSAGE TO SCHEDULE A DATE FOR A 30 MINUTE TRAINING.
------- Continuous glucose monitoring systems (CGMS) ------
There are two primary free-standing CGMS which are quarter-sized devices that are taped on you to provide blood sugar readings without a fingerstick each time. Each system has its pros and cons. We would like you to try both out to determine which is most affordable and best for you.
COMMERCIAL INSURANCE PATIENTS (non-Medicare):
1) Both the Freestyle Libre & Dexcom G6 systems can be sent to your local or mail-order pharmacy on file. Please contact your pharmacy after 10-14 days if you have not heard from them. If the prescription is denied at your pharmacy (this happens ~50% of the time), you may still have coverage through a durable medical equipment (DME) supplier especially if you inject insulin at least 3 times daily. Contact our office or Dexcom (see below) if you receive a denial at your pharmacy and we can help to connect you with an in-network DME supplier.
2) Patients can also initiate the request by calling Dexcom at 1-888-738-3646 and placing an order. You will need to provide Dexcom with your provider's name and fax number. Our fax number is 713.795.0855. Your last office visit with the doctor must have occured within the last 6 months and the doctor should have already discussed CGM therapy with you.
MEDICARE PATIENTS (covered for patients who are injecting insulin at least 3 times daily):
1) For a Freesyle Libre, patients should call 1-855-632-8658 and tell them to send Houston Thyroid and Endocrine a fax with the request for order. Our fax number is 713.795.0855. Your last office visit with the doctor must have occured within the last 6 months and the doctor should have already discussed CGM therapy with you.
2) For Dexcom systems, you should initiate the request by calling Dexcom at 1-888-738-3646 and placing an order. You will need to provide Dexcom with your provider's name and fax number. Our fax number is 713.795.0855. Your last office visit with the doctor must have occured within the last 6 months and the doctor should have already discussed CGM therapy with you. If you have trouble connecting with a Dexcom representative, you can also send a message to our diabetes educator (Katie Spence) in your patient portal or call 713-337-2187. You should include in your message that you are interested in a new Dexcom prescription and she will assist with a Dexcom referral on your behalf.
TRAINING: Once a commercially insured patient has received a device they can request a virtual televisit for training. Please send a portal message. Medicare patients should contact the device company for training.
Comparisons of Each System
Dexcom system:
Sensor lasts 10 days and is waterproof.
Taped on your abdomen (can also be used off-label on back of arm, outer thigh, upper buttocks).
New reading to receiver or smartphone every 5 minutes
Proactive Personalized alerts on receiver or phone
G6 version is pre-calibrated so NO finger sticks anymore, just like Libre
In order to set up an in-person training with a Dexcom representative, patients can contact Dexcom CARE at 1-877-339-2664 Mon-Fri 7:30 AM-10 PM CT or email patientcare@dexcom.com .
Houston Thyroid and Endocrine can set up a virtual training in the office and in some cases at your home (not for medicare or humana or aetna patients)
Freestyle Libre
Sensor lasts 14 days
Taped on your arm (off-label use on abdomen, back of arm, outer thigh, upper buttocks)
Glucose can only be viewed by scanning the sensor
Device is factory-calibrated and does not require fingerstick calibrations
Generally lower cost than Dexcom
There are now two Freestyle Libre systems: Libre & Libre 2.
Libre: Blood glucose alerts: No, only if the user happens to be scanning the sensor. Readings provided every: 5 minutes, Compatible with smartphone: Yes
Libre 2: Blood glucose alerts: Yes, even if user is asleep/not scanning the sensor. Readings provided every: 1 minute, Compatible with smartphone: Not yet, separate monitor is required.
Most patients are able to self-train by using the detailed tutorial videos available online at https://www.freestylelibre.us/support/overview.html . If they want to meet with a rep, they can call 1-855-852-4527.