A continuous glucose monitor (cgm) is a wearable sensor that tracks you blood glucose 24/7 in real time and transmits it to a receiver which can either be a separate unit or your smartphone.  It’s time for doctors and practitioners to get comfortable ordering cgms for their patients.  We are eagerly anticipating the release of cgm devices that are even more portable, less invasive, accessible, and affordable, but in the mean time there are individuals who need this type of monitoring to take ultimate control of their health.

I’ve been a health tracker/hacker for many years, but put off wearing a cgm because I was afraid it would make me even more obsessive about my health than I already am. However, my general philosophy is that I should personally test and try interventions (within reason) that I recommend to patients and my audience, which makes me a far more reliable resource when questions come up.

For this post, I’m going to focus more on the Dexcom G6 cgm device since I’ve had the most experience using this with patients and I decided to test this unit myself.  However I know plenty of people (and patients) who have successfully used the Freestyle Libre cgm device and will share information on that as well.  There is a newer cgm on the market that collects 90 days of continuous glucose data called Eversense, which apparently has a more economical start-up plan, but I have no experience or feedback regarding this device.  The main catch is that the Eversense monitor needs to be inserted and removed by a physician.  Please reach out to me if you have any experience with this device or others and I’ll continue to update this post.

Why Use CGM?

CGM was developed for type 1 and type 2 diabetics who require insulin.  Insurance almost exclusively covers cgm for these indications, but the tide is starting to turn as I’ve seen a rising number of my patients with type 2 diabetes not on insulin or even those with prediabetes get their cgm covered.   Check with your pharmacy to see if your plan provides coverage.

Endocrinologists are intimately familiar with prescribing cgm devices for their patients on insulin (mostly type 1 diabetics), but only recently are primary care doctors and other practitioners being asked to prescribe cgm for patients who are not on insulin, but simply want to use cgm as a behavior change tool.  I have been prescribing cgm for a few years now and only recently decided to use one myself.  Prior to cgm, I had been tracking my fingerstick glucoses for several years to really learn about how my body responds to different foods and lifestyle conditions (sleep, stress, exercise, etc.).  As a result, the cgm data did not provide any unique revelations to me, but definitely kept my behavior in check.  Below are some of the reasons I think cgm can be a powerful tool:

  • Getting real time visual glucose data curbs behavior better than any other tool I know of
  • You get direct, personalized information on how your body reacts to specific foods, which varies among individuals
  • It highlights how non-nutritional factors like your bedtime, your sleep quality, and your stress levels can wreak havoc on glucose, even if your diet and exercise regimen is optimal
  • It actually gets you to move more.  Watching your glucose number rise after a meal or snack really motivates you to get a walk in to limit your glucose spike.  This was the most powerful effect on me.  I had my Dexcom CGM connected to my Apple watch and after a higher carb dinner I watched the number rise like a speedometer which forced me out the door for a quick 20 minute walk!

How to Convince Your Doctor to Order a CGM

A cgm is incredibly easy to order, but doctors are often resistant to doing so for a few reasons:

  • Guidelines: Many doctors don’t like to deviate outside of standard practice guidelines and cgm is not officially indicated yet unless you are on insulin for type 1 or type 2 diabetes
  • Overwhelm: Doctors are already overwhelmed with all kinds of data, so the thought of you sharing weeks or months of cgm data is not appealing.  As a former primary care doctor who used to see patients every 15-20 minutes, I don’t blame them for feeling this way.
  • Device Troubleshooting: Related to doctor overwhelm is the fact that most people will need some initial troubleshooting done to get the device working right.  Doctors who already get plenty of phone calls and e-mail messages for clinical and administrative issues will not want to become a cgm support line.  Again, I totally empathize here and I also encourage these questions to be directed to the vendor who has more knowledge and content in this area.
  • Prior Authorizations:  Until cgms are routinely approved by insurance, MD prescriptions for cgm are often denied and then pharmacies/patients usually request a prior authorization process to be initiated.  I will be frank in telling you that doctors and their staff hate putting in prior auths unless it’s for a medication or device that is truly deemed clinically necessary.  It can be a big time drain for clinical staff who have to fill out forms and spend time on the phone with insurance companies and pharmacies, rather than attend to their primary role, which is direct patient care.  To make your doctor’s life easier, reach out to your insurance or pharmacy directly to determine the specific criteria for coverage.  If they say it’s only for diabetics on insulin, then you may just want to politely ask your doctor for the prescription and just pay out of pocket.  I have never had an insurance company accept a prior auth for a cgm if a patient did not meet their standard criteria.  See section on costs later in the post.

Some resources to make it easier for your doctor:

Dexcom CGM:  This site has specific information on how MDs can order/prescribe the Dexcom CGM for patients.  There are essentially 3 items that need to be ordered.

  1. The Dexcom receiver:  This is the device that provides the glucose readings and the usual life is one year.  This comes as a 1-pack.
  2. The Dexcom transmitter:  This is attached to the sensor (see next) and needs to be replaced every 3 months.  This comes as a 1-pack.
  3. The Dexcom sensor:  This is the actual unit that sits on your skin to sample your blood for glucose.  Each sensor lasts 10 days and this comes as a 3-pack, so it is a 30 day supply.

The image below shows the 3 different units.  The dark screen on the left is the receiver which sits next to a smartphone which can be used in place of the receiver (discussed later under cost).  The large plastic device on the right is the applicator which lightly “staples” the sensor (not pictured) under your skin, and just left of that is the small transmitter which is inserted onto the sensor and basically transmits your glucose data from the sensor to your receiver or smartphone.

FreeStyle Libre: This site and this site have excellent information on how MDs can order/prescribe the Libre CGM for patients.  As these links indicate, your MD would order 2 items:

  1. One FreeStyle Libre 14 day reader:  This is analogous to the Dexcom receiver and provides your glucose readings.
  2. A 28-day supply of 14 day sensors, so 2 sensors required to cover the month and then refills as needed (aka “PRN”)

The 2 units for the Freestyle Libre are pictured below.  You have the reader on the left which is analogous to the Dexcom receiver and similarly can be replaced by your smartphone.  Next to the reader you have a picture of 2 sensors.  So unlike the Dexcom, this system has 2 units rather than 3.

Again, refer to the links and the manufacturer website for details and each of these sites has a specific “prescriber section” which makes it really easy for doctors to order the CGM supplies.  If your doctor uses an electronic health record (EHR) system like Epic, he/she can enter these orders into the system and the order can be sent electronically to the pharmacy just like any medication.  I actually have these orders saved in my Epic EHR so with just a few clicks, I can easily order them for patients.

I also created a cgm agreement for patients and health care providers to more specifically outline expectations on both ends.  This is not a legal document, but may help if you have a provider who is hesitant to prescribe a cgm.  Click on link below.

CGM Agreement for Patient-Providers

Monthly Cost for CGM

The good news is that although in the recent past, my non-insulin users were not getting insurance coverage for their cgm, now things are starting to shift.  I’m actually seeing some of my patients get it covered who are not on insulin, which is great news.  I’m not going to list the insurance products that cover the cgm because those are always in flux.

I called Costco on 2/26/20 and below are their out-of-pocket prices:

  • 3-pack of sensors (30 days worth): $385 and each sensor lasts 10 days
  • Transmitter is $278 and lasts 3 months, so $93/mo
  • Receiver cost is $418, but you don’t need this if you have a compatible smartphone (unless type 1 diabetic).  Verify that your smartphone is compatible.

So together, monthly cost of above sensor + transmitter is $478/mo, excluding the purchase of the receiver which is optional if you choose to use your smartphone.

For the Dexcom receiver and Libre reader (see below), you can use your smartphone as the glucose reader in which case you can save on the cost of purchasing a receiver/reader.

However if you are a diabetic on insulin, it is worth having a receiver/reader unit in case there are issues with your phone.  Many diabetics on insulin also travel with the receiver/reader if they are going to places where smartphone reception might be spotty.  Since I was using this for health tracking, in retrospect I wish I hadn’t purchased the receiver which is non-refundable.

I called Costco on 2/26/20 to check on the out-of-pocket cost for the Freestyle Libre and it was considerably cheaper:

  • The 14 day sensor is  $70, so a 1 month supply (2 sensors) would be ~$140
  • The reader $80, but as already mentioned, you may opt to use your smartphone App instead.  Again check that your phone is compatible.

So based on this, the monthly cost for the Freestyle Libre would run you ~$140 which is considerably cheaper than the Dexcom CGM.  You might just choose to do a 14 day experiment in which case you would just pay $70 for the sensor and use your smartphone for the readings.

For either cgm, it’s best just to contact your local Costco or pharmacy to check on prices.  I’ve also heard Walmart can be economical and there are also online sites like GoodRx, so if cost is an issue, shop around.  You may also choose to purchase directly from the manufacturer, but prices may run higher.

Which CGM Should You Choose?

This is a tricky question.  In the early days, it seemed the Dexcom was superior in terms of accuracy, but now I’ve talked to patients, colleagues and read online forums vouching for either.  Given the big difference in price, you might opt to try the Libre first, perhaps just purchasing the 14 day sensor.  Be sure to also purchase a standard finger stick glucose monitor so you can confirm accuracy.  If any of you have done a more detailed comparison, please shoot me an e-mail and share your experience.

Quick Guide to Getting Started

I originally thought I would post a short video of me setting up my cgm device, but frankly there are far better videos out there on the manufacturer site and their customer support line and resources are excellent.  Also since devices keep getting upgraded, my video would be quickly outdated.

Don’t be intimidated.  The sensor insertion makes some people nervous, but it is really just a light pinch or quick sting that is far less painful and intrusive than a blood draw or a flu shot.

My Overall Impression of the Dexcom G6 CGM

I went into this with very high expectations and although I was impressed with the G6, the experience and device for me was far from perfect.  By the way, I will demo the Libre some time in the future and update this post.  I’ve checked finger stick glucose for years and although there is an initial calibration period for the cgm, even when it was working at its best, the level of precision for me wasn’t where I wanted it.  I do recommend people keep a regular blood glucose meter on hand for comparison’s sake.

I changed site locations on my abdomen and tried my arm as well.  The arm is not officially recommended, but there are plenty of individuals on Youtube and the blogosphere who have had success with this location.  I know if I had persisted, I would have found a more optimal location.  There’s no way a device like this would be approved by the FDA for diabetics on insulin if the transmitted data was not reliable.

I’m just warning you that you may not get precise readings right from the start and there is an initial adjustment period for the sensor which the manufacturer clearly explains in the instructions.  You might be reaching out to customer support a few times to get this right.  For others it can be seamless from the start.

I stopped using the cgm for a different reason.  I’ve been tracking my own health data for over a decade now to get insights about my own body that I can learn from, and share with others.  Although it has been an insightful, educational process, continuous tracking also creates undue anxiety and stress for someone who is borderline “Type A” already.  I also don’t like having something attached to my body 24/7.

Now some of us need 24/7 monitoring to get our act together which is why I am a strong proponent of using cgm in clinical practice.  However if you have already met all or most of your health goals and you are living your life at the mercy of the monitor, you may want to consider stopping its use or at least give yourself intermittent “cgm holidays.”  I will likely slap it back on in the future as I test out different lifestyle interventions, but for now I enjoy not having the feeling of a sensor attached to my body at all times.  I personally prefer intermittent monitoring of my finger stick glucose and ketones as mentioned, especially after my diet and lifestyle fall off track.  I use Keto Mojo for this, but there are other monitors out there that measure both.

You need to have the ability to not overreact to individual glucose readings and instead think of the larger comprehensive snapshot.

For example, a glucose spike after a typical meal or even after high intensity exercise is common and usually normal.  Obviously the intensity of those spikes over time has significance, but you are aiming for your average glucose over time to be within range.

I tell my patients you treat your glucose numbers like stock prices.  Just like you shouldn’t panic  and overreact with episodic market fluctuations, you should have the same attitude with your glucose.  Fortunately these devices have excellent software to display your data over time so you can pay attention to glucose/market trends and make more sensible long-term lifestyle choices.

Also, do not ignore the non-nutritional factors that have profound effects on glucose like eating times, bedtimes, sleep quality, and stress to name a few.

Remember, diabetes is a chronic disease that causes death and damage when there is persistently elevated glucose levels in your bloodstream over a period of years, not days.  The exceptions are the less common hyperglycemic diabetic emergencies with more severe glucose elevations like DKA (diabetic ketoacidosis) and HHS (hyperglycemic hyperosmolar states).  Be rational with your data, analyzing longer-term lifestyle and glucose patterns, and then make meaningful changes accordingly.