Mike Hoskins

Despite what the powers-that-be mandate, I often use my Dexcom continuous glucose monitor results to make insulin dosing decisions... without doing a fingerstick to confirm the results.

((Enter gasps here))

According to FDA regulators and physicians, we're supposed to double-check our BG results by taking fingerstick test before making treatment decisions. While many patients skip that step and make dosing decisions directly off CGM results, that's officially viewed as "off-label use" and therefore taboo.

Hopefully, this is about to change.

The FDA is now paying close attention to this topic, holding a landmark meeting this Thursday, July 21, to determine whether CGM should be officially labeled as safe for insulin dosing decisions.

#DoseWithCGMAnnounced a few months back, this all-day meeting came as a surprise despite the fact that Dexcom has been talking with regulators about this issue for more than a year. At the annual ADA meeting in June, Dexcom released study data showing safety and efficacy of a CGM "non-adjunctive claim" (meaning CGM is good enough to replace fingersticks). That helped set the stage, along with independent studies like the Replace BG Study currently underway on this very issue.

Why is This Important for Diabetes Care? 

Medicare Coverage: While this week's FDA meeting will not specifically address insurance coverage issues, the potential outcome is a strong argument for better coverage of CGM devices among the patient population -- particularly when it comes to Medicare coverage of CGM. To date, the Centers for Medicare and Medicaid Services (CMS) still considers CGM technology to be "precautionary" and therefore not medically necessary. Our D-Community has been actively advocating for change on this front for over two years now. Apparently, one of the paths to getting Medicare CGM coverage is to obtain this dosing designation, so that CGM use becomes as medically necessary as fingersticks are now.

Expanded Use: On a related note, this would allow CGM to get into the hands of more people with diabetes who need and want it, particularly those with T2 who take insulin. CGM's value is that it paints a full picture of how blood sugars are faring, compared to the momentary snapshots fingersticks offer. So if doctors can prescribe CGM for dosing decisions and it's not "off-label," that means more folks will have access to improved care.

Future Tech: This week's meeting is an important milestone with implications beyond just the Dexcom G5 product. A key example is Abbott FreeStyle Libre that's currently only available outside the States but will hopefully be approved here soon. Libre is a no-fingerstick calibration CGM tool, and we're assuming FDA has been considering a dosing designation attached to the product before approval -- so making a ruing on this issue soon could play a part in how quickly Abbott Libre becomes available here.

We're Already Doing This: It's impossible to overlook the fact that many of us are already using CGM this way, so it just makes sense for FDA to keep pace with the patient community's real-world use.

Advocating for Fingerstick Replacement

Our friends at the diaTribe Foundation and Diabetes Patient Advocacy Coalition (DPAC) have both taken the lead on community advocacy on this issue, each preparing a comprehensive letter to the FDA and collecting signatures for our community.

Actually, the FDA flat-out challenged our community during a June webinar to collectively raise our voices on issues just like this. They suggested gathering at least 5,000 signatures, and we're already surpassed that with upwards of 8,000 signatures (!) on the diaTribe letter and many thousands in a similar DPAC letter to the FDA. Obviously, the more signatures from our D-Community on this, the better, and we can still shoot for a nice round 10,000 names... So be sure to click here to sign the diaTribe letter and DPAC letter if you haven't already!

You can also use social media to share stories and keep tabs on this topic, using the Twitter hashtag #DoseWithCGM.

Unfortunately, a live-streamed webcast of this Thursday's FDA advisory panel meeting Thursday isn't guaranteed, but we're told that an audio call-in number will be provided. We plan to tune in, but it may be a bit challenging to catch everything since the meeting runs all from 8am to 6pm EST. Luckily, one of our 'Mine correspondents will be attending in person, so look for our coverage post-event. 

My Personal #DoseWithCGM Experience

In the meantime, #WeAreNotWaiting for the FDA. Yes, I am using my Dexcom data to dose.

We're clear that this is a personal decision and that not every patient trusts the accuracy or reliability of CGM for this purpose just yet. Wee also acknowledge that an FDA designation for this labeling does not require anyone to use a CGM for dosing, as you can continue to confirm with fingersticks if you want to.

While Your Diabetes May Vary and experiences with sensor accuracy differ, I personally have no qualms about using this tool in my diabetes management beyond its current product labeling.

At the end of last year, I actually performed an experiment comparing my meter and CGM results. Out of 130 fingersticks, my Dexcom G4 was within 30 points of my meter reading, and most of the time it was within 10 or 15. That's 89% accuracy, which is good enough for me.

Sure, there are times when I don't trust the results, including:

  • Usually within the first 24 hours while a CGM sensor is warming up, I find it can be widely inaccurate
  • The ending days are often the same, sometimes as much as 24 hours before the sensor poops out (keep in mind that I often regularly wear my G4 sensors past the 7-day mark they're approved for)
  • When higher-carb meals or stressful situations throw my blood sugars onto the glu-coaster, it sometimes takes Dexcom a bit of time to connect the dots and figure out what's happening
  • Also during Lows, I've found my G4 tends to read as much as 20 points lower when I'm under 100 and it takes some time for to catch up to hypo rebounds

Still, I've navigated these nuances and learned from trial and error, and as such my Dexcom CGM is a valuable tool helping me keep my diabetes in check, and that includes using it for dosing decisions.

I even remain reliant on my Dexcom when I'm feeling under the weather (aka: Real Person Sick, that has nothing to do with diabetes). I'm not going to get into specifics today, but let's just say that my blood sugars have been higher than normal this past week, requiring a higher basal dose and some more frequent fast-acting corrections. But that didn't diminish my trust of the D-data being displayed on my Dexcom G4, and I used that to dose insulin along with other decisions.

So in short, we hope the FDA seriously considers the scientific data showing CGM is as good as fingersticks, and listens to our patient community, calling for them to catch up with real-world use of these products.

After all, FDA should know by now that a "Don't Ask, Don't Tell" approach is not practical and doesn't help them keep up with the realities of modern D-care.


[Editor's Note: I have copied this post onto official letterhead, signed it, and emailed if off to the FDA for consideration on this issue.]

Disclaimer: Content created by the Diabetes Mine team. For more details click here.


This content is created for Diabetes Mine, a consumer health blog focused on the diabetes community. The content is not medically reviewed and doesn't adhere to Healthline's editorial guidelines. For more information about Healthline's partnership with Diabetes Mine, please click here.