Choosing a CGM: 3 Heads are Better Than One

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What CGM systems are available in 2018?

Question:  what do Cerberus (the hound from hell), Chimera (the fire-breathing beast) and the backfield for the Super-Bowl-winning Phiadelphia Eagles have in common?

Answer:  All are 3-headed monsters capable of kicking some serious butt.

Why bring this up in a diabetes blog?  Simple.  The world of diabetes is chock full of 3-headed monsters.  We have three insulin makers, three dominant meter manufacturers, three pump companies, and for the first time, three companies producing CGMs (continuous glucose monitors).

Competition is definitely a good thing – it keeps all parties on their toes, striving to innovate, improve, and serve the customer in the best way possible while keeping costs down.  But having multiple options can make everything seem a bit more confusing.  There is no doubt that CGM can improve the quality of life and blood sugar control for just about everyone with diabetes.  But which system is best for you?

When making a choice, it helps to understand what each system has to offer:  the good, the bad, and the ugly (see – another threesome!).  We do our best here at Integrated Diabetes Services to remain fair & impartial when it comes to these types of comparisons.  We also try everything out personally before recommending anything to our patients.  So here are some facts and observations that might help you to become a more educated consumer.

 

THE THREE HEADS

Presently, personal-use, CGM systems are available from:

  1. Dexcom
  2. Abbott
  3. Medtronic

Dexcom’s system, called G5, will be replaced in the summer of 2018 by the G6 (don’t you love the creative names?).  G5 and G6 have many characteristics in common, but G6 offers a number of advantages, so we’ll discuss both.

Abbott’s system, called Freestyle Libre, was introduced in the US earlier this year, and has been available in other parts of the world (albeit a slightly different version) for the past several years.

And the latest entrant, Medtronic, is on the precipice of introducing the Guardian Connect system, a CGM that is not linked to a pump and can be used by just about anyone.

 

HEAD TO HEAD COMPARISON: The Latest Continuous Glucose Monitors

Dexcom

Dexcom is the system that most people are familiar with and has become somewhat synonymous with CGM.  The Dexcom G5 (to be replaced by the G6 in mid-2018) features a comfortable, easy-to-insert, long-lasting (approved for 7 days, most get about two weeks of use) sensor that produces the most accurate data in the CGM business.  Following a two-hour warmup period (during which data is not available) and initial fingerstick calibration, G5 asks for fingerstick calibrations at least once every 12 hours.  It continues to provide data even without the calibrations, but regular calibration is necessary to ensure ongoing accuracy.

 

The MARD (average difference between sensor values and lab values) is around 9%, and Dexcom clearly outperforms the other sensor in terms of accuracy when glucose levels are in a low range.  The re-usable transmitter emits a signal that carries approximately 20 feet, has a 3-month battery life and does not require any kind or charging or other maintenance.  The receiver displays the data (current glucose values updated every five minutes, trend graphs and rate-of-change arrows) and emits alerts (customizable beeps or vibrations) for pending high/low glucose values.  The high/low alerts can be customized by time-of-day.  The receiver can take the form of a handheld touch-screen receiver, a smart phone (iPhone or Android), or Tandem X2 insulin pump.  Those using a smart phone can have the data transmitted for viewing on a smart watch.  Because the data generated by G5 is stored in the cloud, loved ones have the option of seeing live reports on their cell phones and receiving alerts in the event of potential problems.

G5 transmitting to an iPhone

Dexcom’s recently approved G6 will offer everything G5 has to offer, plus a number of new benefits:  An even simpler 1-button insertion process, a flatter-profile sensor/transmitter, vastly improved day-1 accuracy, a 10-day sensor usage cycle (compared to the current 7-day cycle), a sensor that is unaffected by acetaminophen (Tylenol), and an optional predictive alert for very low glucose values.  The biggest improvement is that G6 is CALIBRATION-FREE.  No fingersticks are required.  Yet it achieves the same accuracy as G5 WITH calibrations.  Not bad!  However, G6 can accept calibration values in case the sensor is drifting off course and deviating significantly from fingerstick values.  The calibration entry allows the sensor to get back on track and improve its accuracy from that point forward.

Reports can be generated quickly and easily via Clarity software on either a PC or smartphone.  Data and reports can be shared automatically with healthcare providers in a variety of ways.  Dexcom is also compatible with just about every “midware” program (for merging data pump & CGM data), including Tidepool, Diasend and Glooko.

 

Freestyle Libre

Freestyle Libre has some but not all of the features of a traditional CGM.  The sensor and transmitter are combined into one compact unit that inserts very, very, very easily.  After a 12-hour warmup period, the user can “scan” the sensor with a handheld receiver to see a current glucose value along with a trend arrow and graph of the most recent eight hours of data.  The sensor/transmitter is replaced every 10 days (assuming the adhesive holds in place), and no re-use of sensors is possible.  NO fingerstick calibrations are required.  In fact, you CAN’T calibrate Libre, even if your fingersticks values differ by quite a bit from what the sensor is showing.

Libre is relatively inexpensive compared to other CGM systems (about $60 for the durable receiver/scanner, $40 per sensor).

Freestyle Libre sensor and reader

The accuracy of Libre is good despite the absence of fingerstick calibrations.  It has a MARD of about 10%, and the sensors are not affected by acetaminophen.  However, Libre is far less accurate when glucose levels are on the low side, producing false alerts (reading low when glucose isn’t really low) about 40% of the time.  And the inability to calibrate the system can sometimes leave the user with a sensor that runs chronically higher or lower than actual glucose values.

But the major drawback is the lack of alarms/alerts for pending high and low glucose levels.  The user has to physically “scan” the sensor in order to generate any data and see what is going on with their glucose level.  This can expose users to highs and lows any time they are not scanning, such as during the night, between meals, while driving, and when exercising.

Libre also lacks the ability to transmit data to a cell phone or to “share” the data electronically with loved ones and caregivers.  This will likely change over the next several years (there is even a company that is marketing a product to amplify the signal and send it to a smartphone), but for the time being, the only person who can see what’s going on is the one who is scanning the sensor.  Downloading is limited to Freestyle Libre desktop software, which does not merge data from other devices (such as pumps).  However, Libre and pump data can be merged through the Tidepool data management system.

 

Guardian Connect

The Guardian Connect system from Medtronic features the same Guardian sensor that is used with the Medtronic 670G hybrid closed-loop pump.  The sensor insertion process is relatively simple and painless, although the taping process can be clunky and cumbersome.  The transmitter uses Bluetooth technology to send signals to the Guardian Connect app that runs on various smartphones.  After a 2-hour warmup period, glucose readings are transmitted to the app every five minutes.  The sensor is intended for seven days of use, although many people find that they can re-use the same sensor beyond seven days.  However, as was the case with previous versions of Medtronic’s CGM, the transmitter must be removed from the sensor and re-charged on a weekly basis.

 

What’s really different now compared to prior Medtronic CGMs is the accuracy and reliability of the sensor.  When calibrated 3-4 times daily (using a really good meter, such as the Contour Next from Ascensia), its accuracy is close to that of Dexcom:  a MARD (average discrepancy between sensor and LAB values) of 9-10%.  The Guardian Connect App provides the user with high/low alerts that are customizable by time of day.  It also features predictive alerts that can help the user guard against highs and lows up to 60 minutes before they occur.  Although these types of long-term predictive alerts may generate some false alarms, they can also help users to spend more time within a safe target glucose range.

Another cool thing about Guardian Connect is… well… connectability.  Data from the app uploads automatically into Medtronic’s Carelink software.  This allows quick, easy access to a variety of reports by users as well as their healthcare providers.   Plus, loved ones can receive alerts via text message on their smartphones whenever trouble arises.  Medtronic has also developed a new feature for users:  Sugar IQ, a data analysis system that points out how everyday activities affect glucose levels.  Of course, this will require logging information into the app, and there’s no telling whether it will generate truly useful/applicable observations, but the prospect does sound interesting.

Dexcom G5/G6 Freestyle Libre Medtronic Guardian Connect
MARD (lower number means better accuracy) 9% 10% 10%
FDA Approved For ages Age 2+ Age 18+ Ages 14-75
Calibration Required? G5 – yes – 2x daily

G6 – NO, but can calibrate if sensor is off-track

No, and not possible Yes – 3-4xdaily
Sensor Life G5: 7-14 days (or more)

G6: 10 days

10 days 7 days
Warmup time

(New Sensor)

2 hours 12 hours 2 hours
Transmitter Lasts 3 months, no recharging Fresh Transmitter connected to each sensor Must re-charge weekly
Display options Smart phone

smart watch (via phone BT connection),

Tandem X2 pump

Handheld receiver

Handheld scanner Smart phone

Smart watch (via phone connection)

Hi/Low Alerts Yes, customizable None Yes, customizable, including extended predictive alerts
Live Data Sharing Yes – high/low alerts and current glucose level/trend None Yes – high/low alerts
Downloading/Data Analysis Automatic upload to Clarity software.

Compatible with most midware programs for merging data with other devices (Diasend, Glooko, Tidepool)

Freestyle Libre software

Tidepool (midware)

Automatic upload to Carelink Software

Sugar IQ program for analyzing data

Cost/Coverage Approx $300 per transmitter

$80 per sensor

$600 per receiver

G5 covered by Medicare and most private insurance plans

Approx $60 for scanner

$40 per sensor

Covered by Medicare and most private insurance plans

Approx $1000 per transmitter

$80 per sensor

Coverage Pending

 

CHOOSE YOUR HEAD

Unlike choosing which of Cerberus’s heads is going to turn your head into its own personal lunch, choosing a CGM is really a no-lose proposition.  You will undoubtedly benefit from any system you choose.  However, as is the case with insulin pumps, certain ones may be a better choice for you personally.

DEXCOM G5/G6

DEXCOM G5/G6 is a great option for anyone who wants a reliable, proven system that is simple and flexible – particularly those who are treated with intensive insulin therapy.  The customizable high-low alerts and “sharing” features make it ideal for those trying to ward off serious hypoglycemia.  Although the sensors are a bit pricey, the ability to re-use them (until they stop working properly) helps keep the cost down.  Those looking to improve their diabetes management and spend more time within their target range can certainly benefit.  Dexcom is also in cahoots with a number of companies developing hybrid closed-loop systems, so use of Dexcom now creates a more seamless transition to future technologies.

FREESTYLE LIBRE

FREESTYLE LIBRE is a nice choice for those who are at little risk of hypoglycemia, which includes most people with type-2 diabetes who are not taking insulin.  The prolonged warm-up period and lack of high/low alerts can leave the user vulnerable to dangerous glucose levels.  Also, the inability to calibrate the system may frustrate users who micro-manage their insulin and demand a high degree of accuracy.

It can also be a reasonable option for those who are easily distracted or annoyed by the alarms/alerts generated by the other CGM systems.  Finally, Libre is a good option for those who must pay out-of-pocket for their equipment and supplies.  The scanner costs a fraction of what the “hardware” costs with the other systems, and the sensors cost about half.

MEDTRONIC GUARDIAN CONNECT

MEDTRONIC GUARDIAN CONNECT carries the Medtronic name, which means different thing to different people.  The company invests a ton in research & development, and is financially secure for the long-haul.  Medtronic puts a great deal of its resources into “what to do with the data.”  Their Carelink program and new Sugar IQ algorithm can be instrumental in helping users (and their clinicians) learn from the data and make therapeutic adjustments.  Technically-oriented users may enjoy these and other features of the Medtronic system.

 

Because out-of-pocket costs guide many of our health care decisions these days, it may be helpful to know that the Dexcom G5 and Freestyle Libre are covered by most private and public health insurance plans (including Medicare).  Medtronic and Dexcom G6 should be covered by most private plans, but not yet by Medicare.

 

To learn more about the various CGM options and determine which system best suits you, feel free to contact our office and schedule some time with one of our CGM-wearing CDEs.

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18 Comments

  1. Silvia Bueno April 23, 2018 at 10:11 pm - Reply

    This is an excellent article. I recently did all this research on my own. The cost for the Medtronics CGM was out of the question for me because of its cost, even though it’s probably the best closed loop for the Medtronics pump.
    Since now I’m on Medicare, I had to really decide between the Dexcom & Freestyle.
    Since I’ve been on the pump for about 20 years and monitored my sugar aboutv6x/day, I did not want to be bothered with all the alerts.
    Since I have the Libre, I check my blood sugar twice as much now and it’s so much easier for me. I feel much more in control and my AIC is finally under 7
    Enjoy your CGM no matter which one works better for you.
    Both the Dexcom and Freestyle are covered by Medicare, and the Dexcom, I believe can communicate with the Tandem pump.
    Silvia

  2. Silvia Bueno April 23, 2018 at 10:13 pm - Reply

    Love my Freestyle Libre

  3. Louise May 27, 2018 at 5:07 pm - Reply

    Thank you for the GREAT article. My Medtronic insulin pump is up next February and I’m looking. Pump is great. CGM helped me learn what was happening in my body the first year or so. But issues with readings and 6 days at most for me of accurate readings was very frustrating. Have been able to stay close to 7 without it so gave it up a few years ago. But I really miss the predictive lows (Type 1 for 51 years) so hoping Dexcom G6 and pump will be better for me. Really appreciate the thorough review and great highlights!

  4. Hosam El Nagar July 13, 2018 at 11:47 pm - Reply

    Thanks for the great article..
    but as always.. people living outside the us are having a tough time living with t1d and no luck at all with any of these companies.
    I live in Egypt.. and I have to tell you.. managing my diabetes is extremely hard while I can barely afford my pump disposables and such..
    and to top that off.. most of the said companies dont even bother getting their cgm systems here at all 🙂
    hope this changes some day…

    • alicia downs August 29, 2018 at 2:03 pm - Reply

      Hosam, we agree! We work with patients around the world and it can be really difficult to get the care, medications and technologies needed.

  5. Kathryn July 24, 2018 at 8:16 pm - Reply

    I have the Libra BECAUSE I am reactive hypoglycemic on top of early LADA. I also pay out of pocket. The Libra drove me crazy because it was so inaccurate and could not be calibrated. Solution? I now use a MiaoMiao to read it every 5 minutes (an upgrade from the NightRider I initially bought) and the Spike app for I-phones so I can calibrate it. The only thing I don’t like is that I can’t figure out how to store and print out the graphs with all of my notes, but someone a bit more tech savvy probably knows how. This has made a more accurate and cost effective solution for me since there’s no way I can afford either of the other two options.

  6. JJ August 11, 2018 at 5:16 pm - Reply

    Searching online and can’t find the size and weight of each of these to compare. Would be a great addition to this article to compare. I’d imagine the longer the battery life and/or addition of bluetooth the larger the transmitter.

    • alicia downs August 29, 2018 at 3:16 pm - Reply

      great question, we will look into these specs. They are all relatively the same mass and cover roughly the same area, but the exact differences would be interesting.

  7. beepee August 19, 2018 at 3:50 am - Reply

    Great article, but here’s a thought about ‘qualifying’ for Medicare. I’ve been a Dexcom user since the G4 Pre-Medicare days. I am a Senior T2, with T1 dependence after an auto accident left me concussed (Mild Traumatic Brain Injury (MTBI)). This was BEFORE Medicare approval. Well guess what, we can put a man on the moon, but NOW, between my Health Carrier, Dexcom, and Medicare, after a year and eight months (post-Medicare acceptance) I still have never had a “Medicare Bundle” shipped from Dexcom.

    Here’s Why. Dexcom is the ‘defacto standard’ for CGM, but that’s all they do. FreeStyle and Medtronics have a Medical-savvy parent Corp structure that has protocols in place to deal with the likes of “The Government” and the Health Industry in general. Obviously, little ole Dexcom has the dubious ‘instant success’ (with stock jumping through the roof with the G6) of moving up the ladder so quickly that, in spite of having “Medicare Specialist”, and dedicated Health Plan Liaisons on board, they still can’t administratively position themselves to be a efficient as their CGM.

    Don’t get me wrong, when it comes to dealing with the Feds (any entity), it takes some doing, but there will be pain (even for Medicare guys to understand their very own regulations). To understand, you have to make, like me, many, many phone calls to Dexcom, Medicare and my my numerous Health Plans, and talk to many different associates within those organizations, to experience hopelessness of getting different answers and reasoning regardless to virtually the same ‘customer service/care’ questions within that same organization. Something is wrong in Denmark.

    You’d think that the ‘hard part’ would be to develop the CGM, getting it out to diabetics on Medicare should be easy. Since Medicare CGM approval, 18 months ago, I’ve only known of one successful placement of a Medicare qualified CGM order placed of three Endocrinologists I’ve visited – Health Plans just can’t seem to get on the same page with Dexcom, which in turn makes Dexcom even more ‘reluctant’ to submit claims to Medicare, instead of submitting a claim, getting a written rejection, then correcting the reason for rejection, then successfully re-submitting for approval – simple.

  8. mike September 5, 2018 at 5:07 am - Reply

    Im a type 1 diabetic have been since I was 6 ( Currently 41). For years the best I could do was a a1c of 6.7-6.9. most people would say I was in the 6 range and that was good. It was August of last year when I found out my friend ( who was diagnosed with type 2 diabetes in 2000 ) had went completely blind, lost some toes and is on kidney dialysis all this had happened About 5 years ago. It was devastating to see him like this ( he was not overweight ). However he did not check his blood sirgars how he should and it finally caught up to him. It was about that same time last year I started getting a warm sensation in my feet. After this I wanted to get as radical as I possibly could with the a1c. I had been checking my blood about 12;times a day and was so tired of trying to stay ahead of the game I researched and got a dexcom. I set the low level at 70 and the high at 130 and have watched my carb intake to a new degree. Within 3 months, my A1c had dropped to a 5.8!! You read that right the warmth in my feet is gone and has not returned in the past year, my levels are now at 5.8- 6.1. The Dexcom is a huge benefit for me and I think every diabetic should get some type of cgm.

  9. Dith September 18, 2018 at 1:14 pm - Reply

    After 11 days with the G6, I am not impressed. The new receiver is HUGE compared to the G5. I am consistently places where cell phones are not allowed, so am reliant on the Dexcom Receiver. It does not fit into the pockets of ladies slacks nor can it be attached to a waistband.
    The pop-up 1, 2, okay menu when there is any kind of alert or need to access the menu is beyond annoying. I have my numbers set to very narrow parameters to give me tight control of my glucose level. (My last A1C was 5.2.) I want to see not only the current glucose number but the trend line. To do this, I have to tap, tap, tap the screen. Once the trend line is visible, there is still more tapping to get to the correct trend line. There is much less choice here.
    The readings on the G6 are no more accurate than those of my G5. I am still doing finger sticks occasionally to check the accuracy. I am also having issues with multiple signal losses that I only occasionally experienced with the G5.
    The transmitter is only negligibly smaller. One end of the G6 is a tiny bit smaller; the other end is exactly the same size. The sensor is actually larger for the G6 than the G5.
    I experienced very little pain with insertion of the G5 so am not impressed with the “less pain” touts for the G6. The first sensor bled so much that I didn’t think I would ever get all the blood off the transmitter when I removed it after 10 days. The second insertion was VERY painful and also bled. This is something that I rarely experienced with the G5.
    The G6 sensors do not adhere as well as the G5. I removed the first G6 an hour early to get myself on a better schedule than the one that resulted from the upgrade kit arriving late. Even removing it early, the sensor was already starting to peel off. This despite the fact that I use Skin Tac. When I inserted the third sensor (more to this story below), it did not adhere would probably have fallen off early if I had not had to remove it due to failure of the system. Again, this is despite the fact that I use Skin Tac.
    So, now for the real news. After removing the first sensor, inserting the second G6, and beginning the 2-hour warm up, I received a message that there was a sensor error, please wait. So I waited. In about five minutes, I received a message that the sensor had failed. “Replace it now.” So I did, inserting my last sensor! The same thing happened with the third and last sensor. I immediately called Dexcom support and spoke with a very nice representative that informed me that “this has been happening to other users, too.” After over an hour on the phone (not counting the 50 minutes on hold just to speak with a rep), she informed me that there was nothing else she could do. They would ship 2 new sensors to me overnight deliver. BUT!!!!! The supplies are low and there will be about 7 days before they even ship the thing! Of course, she assured me, once it is shipped, it will arrive the next day.
    This rep also told me that there have been many consumer complaints about the new G6 system. Who tested this next generation?! From what I have read inn reviews and been told by the rep, the G6 DOES NOT WORK AS ADVERTISED. I do not recommend the G6. Hopefully Dexcom will fix all the problems before phasing out the G5.
    I will probably spend most of my day on hold today with Dexcom reps trying to go back to the G5 system. Overall, it works much better than the G5. Sure, the receiver requires calibration, but al least it is dependable. I never had problems like this with the G5!

    I have also had major problems getting my supplies from Dexcom. They claim that it is due to the release of the G6. Whatever the reason, when I have to call multiple times for my order, with an average hold time of about 40 minutes, and my supplies arrive on the afternoon of the day my last sensor dies, that is unacceptable.

  10. Shirley Peters September 29, 2018 at 6:20 pm - Reply

    My cvs pharmach was told there is only 12 pharmacies in the USA that is allowed to carry the Free Style Libre. Is this true?

    • Gary Scheiner November 11, 2018 at 3:20 am - Reply

      That may be true, but some are huge pharmacy chains like CVS.

  11. M. C. October 9, 2018 at 2:17 am - Reply

    I’ve used the Dexcom G4/G5 off and on for several years now. There are a few issues with it that I can’t believe the company won’t fix. One is that you cannot turn off the low alarm. In your article you say that it’s a problem for the Pibre that there’s no automatic low alarm. I cannot overstate how wonderful that would be. With the Dexcom, it often has a false low (it tells me I’m below 50 when my body and my meter says I’m at 90). There’s no way to turn it off, which means either I eat something to trick the system but then end up with an avoidable high blood sugar, or I sit and stew while multiple LOUD alarms go off, or I do what I typically do and take the receiver or phone and go hide it in a drawer on the far side of the house. How does that make my life better or control tighter? And all they have to do is make it so that I can turn that alarm off if I want to. I can’t wait for someone to dethrone Dexcom as the “best” CGM company. They don’t seem to care much about their customer’s quality of life at all.

  12. Jessica Parker October 20, 2018 at 10:42 pm - Reply

    This is great info! Just found out I have diabetes by my new doctor that I found through Insurance Line One. Thanks for the info and post.

  13. Teresa Woodall November 2, 2018 at 2:32 am - Reply

    Great article I ‘ve been diabetic for 45 years My first insulin pump was a destronic and took special insulin which most of the time was on back order. Used a minimed next, the Medtronic for 15 years, then Omni pod which I really didn’t like had no control and now in search of something new again. Taking Tresiba and approx. 4 injections of Novolog a day I think I would like to try the Minimed 670G now lets see what my insurance says about this I have worked in the medical field for 26 years and have crappy insurance and this past year had 6,000 dollars out of my pocket and cost me about 900 a month out of my pay check O well I know there are much worse off people out there Wish me luck on my search for a better healthier life.

  14. Michele Cariveau November 11, 2018 at 2:49 am - Reply

    I am trying the Dexcom G6 for a week through my diabetes center. I love it, but the cost, even with insurance, is prohibitive. I’m considering using the Libre system. Even without the real time data, I think it will help lower my A1C.
    My question..why are the Dexcom and the Medtronic so expensive? I understand the companies need a profit, and money for research. However, as many t2s and t1s as is in the population, I think using a cgm would be a HUGE help in in the public health sector, lowering the cost of complications and number of deaths.
    Ah, well..I’ll keep my fingers crossed that sometimes the cost will come down.
    Thank you for the information!

  15. Shree Mulay November 11, 2018 at 2:51 am - Reply

    Thank you for doing this research. So far, this is the only available article I’ve come across comparing the available CGM’s…

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