Libre 3+ vs Dexcom G7 Detailed Comparison

Libre 3+ vs Dexcom G7 Continuous Glucose Monitoring (CGM) systems – a Detailed Comparison of Features

By Gary Scheiner MS, CDCES

It’s not exactly Godzilla vs Mothra, but the epic battle of CGM superpowers features just as much drama and intrigue. 

Just to provide some transparency, I’m a long-time Dexcom user, going back to the original Dexcom STS – 3-day system with plenty of “first generation” issues.

I’ve used every Dexcom iteration since then and have been quite pleased.  I tried the original Libre and Libre 2 a few years ago, but because they required manual “scanning” of the sensor, it was impractical to perform head-to-head comparisons with Dexcom.  But Libre 3 (and now 3+) transmits data continuously to a smartphone app and is approved for interoperability with pumps, so the time is right for a fair comparison.

I must admit, I’m a bit late in reviewing the Libre 3+, mainly because I was waiting to see if it would integrate with my preferred pump/automated insulin delivery system.  Since that hasn’t happened yet, I decided to try it on its own.

Libre Lingo

Abbott has announced plans to discontinue their older-generation Libre sensors as of September 30, 2025, and only offer the 3+. 

The 3+ is approved for ages 2 and up and during pregnancy. It is also designated for interoperability, which means that it can feed data into algorithms that adjust a pump’s insulin delivery.  It shares the same design and features as 3, but is unaffected by vitamin C, which could produce erroneous readings on the 3. The phone app for 3+ is the same as the app for the 3.

Since it does not require “scanning” by the user, 3+ generates continuous data on the phone app and can produce real-time alerts for high and low glucose levels.  It is also built for 15-day wear, compared to 14 with the Libre 3.

Performance Comparisons of the Libre 3+ vs Dexcom G7 CGMs

Earlier this year, I wore two Libre 3 and two Libre 3+ sensors in addition to my usual Dexcom G7.

For comparing system performance, I did not use my own data.  The information below comes from studies conducted by the manufacturers involving thousands of subjects of various ages… so it is widely applicable.  My data would only apply to short, bald, Jewish guys with glasses.

* Dexcom tested their sensors on two different body parts – arm and abdomen – and showed data differences between these sites.  Libre was only tested on the arm.  Dexcom data shown above is based on arm placement.  Performance on the abdomen was slightly worse.

Overall, the performance of the two systems is similar.  Based on the published data, Dexcom may perform slightly better in a hypoglycemic range, and Libre in a hyperglycemic range. But I wouldn’t read into this too much, as individual results can vary considerably.

Feature Advantages of the Libre 3+

THE GOOD:

After wearing the 3+ for almost 30 days, I found several features that I really liked, and some that others may find beneficial. 

1. I particularly like the 1-minute data updates (Dexcom generates a new data point every 5 minutes).  This can be helpful in a number of situations. The 1-minute updates may allow users to catch hypoglycemia a little earlier. After treating lows, Libre shows the glucose rise sooner, which may help prevent overtreatment. Likewise, after correcting a high glucose with insulin, Libre shows the decline earlier, which may help one avoid an unnecessary second treatment.
2. The 15-day wear (compared to 10 with Dexcom) is also nice, assuming that the sensor lasts that long.  According to Abbott’s studies, about one out of five people don’t get 15 days from their sensors – either because they came off or stopped working properly.
3. Personally, I like the way Abbott’s software (Libreview) displays “events” (meal, insulin, exercise entries) right on the trend graphs in the reports.  Dexcom’s Clarity software displays the events in a list under the graphs.  Having the information on the trend graph makes it much easier for me to see cause/effect relationships in my data… and that of my patients.
4. One feature that (technically) gives Libre an edge, but which I didn’t find particularly helpful, is its size.  Libre 3+ is about the size of a penny; Dexcom is the size of a nickel.  Since I gave up wearing leather and spandex a few years ago, it really doesn’t make a difference to me.  But for people who wear very tight clothing, it might.
5. The cost of the systems is a factor that may matter to those without good insurance coverage. Dexcom G7 sensors retail for about $100 each ($300 per month); Libre is about $80… for two ($80 per month).  But note that Dexcom has countered this difference with copay and cash-pay cost assistance for those who have significant out-of-pocket costs (https://www.dexcom.com/savings-center).

Libre 3+ Disadvantages

THE BAD:

Objectively, there are a number of areas in which Libre 3+ comes up short compared to Dexcom G7:

1. The trend graph only displays a 12-hour report. Because so much data is “scrunched” together, it is difficult to see what has been happening over the last 15 minutes.  That immediate/recent trending is very important when making decisions regarding food, insulin, exercise, etc…
2. The alert options are quite limited. As opposed to Dexcom’s app, which offers high/low, predictive and rate-of-change alerts, Libre only has the high/low option.  Libre does not have a “delay first alert” feature to prevent unnecessary high alerts, or does it allow the user multiple choices for customizing the alert tones.
3. The inserter cap is hard to unscrew… At least compared to Dexcom’s. This can present a challenge to those with limited hand strength.
4. There is no way to calibrate. No sensor is perfect, but at least Dexcom gives the user an opportunity to correct the system if it is generating inaccurate data.
5. The urgent low alerts are way too loud. For iPhone users, there is no way to adjust the volume of the urgent low alerts, and they are DISRUPTIVE.
6. The warmup time is relatively long. Libre takes more than twice as long as Dexcom to warm up with each sensor replacement (60 vs 26 minutes), and there is no way to warm up a sensor before activating it.
7. Libreview software comes up short. It does not produce a sensor overlay report (spaghetti graph) report, and it lacks the ability to customize reports by day of the week.  At this point, Dexcom data can be downloaded to a multitude of programs in addition to Dexcom’s Clarity platform; Libre cannot.
8. The trend arrows are poorly defined. Every other CGM system has a specific definition associated with each type of trend arrow (for example, one up arrow means the glucose is rising 1-2 points per minute over the past 20 minutes).  Libre has no clear definitions… just that they represent change over the past hour, with greater emphasis on the past 15 minutes. I prefer to know exactly what is happening.
9. Customer support is not available 24/7. Well, the “7” part is right, but not the 24. If you need to call for technical assistance, it must be between 8am and 8pm EST.  Whoever heard of 12/7 customer support?
10. The shelf life of the sensors is shorter.  Compared to Dexcom sensors, Libre sensors expire sooner after their manufacture date.  This means that your sensors may expire before you have a chance to use them, especially if you receive your supply orders in large batches.

My Personal Slant

After wearing Libre and Dexcom simultaneously for the past couple of months, I can say this: I’M TIRED. 

Not tired of wearing things… I mean physically tired.  Abbott’s false-low-alert frequency may be similar to Dexcom’s (15% vs 13%), but while I was using it, Libre woke me up about a dozen times in the middle of the night with urgent low alerts that were way off (fingersticks and my Dexcom showed normal glucose levels).  On two nights it occurred twice, and there were also several false urgent lows during the day.  And remember, as a user of an iPhone, I could not switch to vibrate or adjust the settings to make the alerts quieter. It was loud enough to wake me, my wife, our four cats, and possibly our neighbors.

Could the false urgent lows have been due to “compression” on the sensor site?  Perhaps, but I wore the Dexcom right next to the Libre on my arm just to be sure – and it performed fine. Could it have been just one faulty sensor?

I suppose, but it happened with both Libre 3 and 3+ sensors I used, and they had different lot numbers. I can put up with some things, but the disruption caused by all those false urgent low alerts was a deal breaker.

Which is a shame, because I thought the quality of the sensor itself was pretty good. Compared to Dexcom, I experienced fewer lost signals and missed data points. Based on my experience with patients, there seem to be fewer “sensor errors” and “failed sensors” with Libre than with Dexcom.

On the flip side, I found Libre’s customer support to leave a lot to be desired.  I called in twice (during their 12 “open” hours) – once for a period of lost data, and the other time to report a false urgent low alarm, just to see what they had to say.

The technician had me turn my phone off and on to fix the lost data (which sounds to me like a glitch with the app). That did the trick. But when it came to the false urgent low alerts, they had no answers, nor did they offer to replace the sensor. Their advice was simply “you should check your glucose with a meter if you don’t think the sensor is trustworthy”.  Excuse me, but why then am I using a CGM???

Dexcom has always been helpful, cordial, and more than happy to replace a sensor that isn’t performing up to speed. They seem to understand how important my CGM is to me and try to make sure I have a good experience. And if my experience is representative of the way most customers are treated, Abbott really needs to do a better job with their tech support.

If anyone else has experience using both Libre3+ and Dexcom G7, I would love to hear your thoughts and feedback.

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