Libre vs. Dex: A Sugar Surfer's Experience

Sugar Surfing™ was born out of asking a question. After adopting an early generation real-time CGM almost 10 years ago, I was also wearing an old insulin pump (Deltec Cozmo). The question I asked was simple: which one of these two devices attached to my body was more important to me? Both were helpful, but which one could I best do without?

After over 30 years of pumping insulin I chose to go back to multi-dose insulin (MDI) and just wear a CGM device. Using the data and trends visible from the CGM, I was able to discern a set of personal self-care guidelines based on close observation of my unique eating behaviors, activity and insulin dosing decisions. What soon became clear was that my blood sugar dynamics were similar, but never identical from day to day. There was always some degree of uncertainty. But since I could visualize the glycemic trend line, I could see these changes before they could come to fruition. It wasn’t long before I was preventing problems before they happened. I would define that as “pre-empting” in the book Sugar Surfing.

Recently, I asked myself another question. After years of Sugar Surfing with a current generation CGM (Dexcom G5 as shown above on the right), how would the Abbott Libre Freestyle (as shown above on the left) system compare? This is not a new technology around the world, but only recently approved for use in the US for real time CGM use in adults.

In the past I had worn two Dexcom CGM units at the same time and compared the results. There were some minor variances even when the units were calibrated simultaneously and inserted at the same time. The experience highlighted to me that every technological device possesses variance, even when those devices are as close to identical as possible.

This time, I simultaneously started wearing a new Dexcom G5 sensor and Abbott Libre (newly approved US version). The Dexcom has a two hour wait time. The Libre in the US requires a 12 hour “warm up”. This is first obvious difference between the two.

Insertion of the Dexcom requires help if worn on the arm…or great dexterity. I use the former. The Libre sensor is much easier to insert. The applicator is spring-loaded, unlike the Dexcom which requires a smooth forceful motion on the plunger. Libre has a relatively pain free insertion. Advantage Libre for ease of insertion. The external sensor housing has a slimmer and sleeker profile. The Dex enters at an angle and is longer, but I can’t speak to how much deeper it penetrates than the Libre.

Adhesives are the bug bear of attachable diabetes tech devices. Reports of allergic reactions to sensor and insulin pump site adhesives are common in the #DOC. In some persons, adverse adhesive reactions can derail use of these tools. There are many homestyle remedies for adhesive allergies and some strategies do help, but some are still unable or unwilling to put up with the additional work of dealing with skin problems with adhesives.

I am fortunate to not have skin reactions to any adhesives. My reputation remains intact with the Libre. Compared to the Dexcom G5, the Libre sensor adhesive strongly attached to my skin well. Both were exposed to the shower at least once and sometimes twice daily. Neither came off or even peeled up. But this observation is invalid since I also apply a second tape layer (IV3000 dressing) above the Dexcom G5 sensor which increases the surface area and holds down the edges of the G5 sensor pad and adhesive. When it was time to remove the Libre sensor after 10 days, it was quite well attached to me and took some effort to remove. The Dexcom sensor unit peeled off relatively easily.

I use an Abbott Freestyle Lite meter to calibrate my Dexcom G5. The Libre requires no calibration; that’s done at the factory. The Libre still has a built-in meter to use when confirming out of range readings. The sensor will prompt the user to check when readings are changing rapidly (up or down) or if they fall outside your programmed target range. The target ranges for both devices are user defined.

The Libre can provide a reading as often as every minute. The Dexcom reports a value every 5 minutes. CGM tech insiders have ways around this, but I will limit my observations to my own experience for now.

The BG trendline screen on the Libre is factory set at 8 hours. The Dexcom screen can toggle between different time windows from 1, 3, 6, 12 and 24 hours windows. This allows for closer inspection of the data stream down to the individual reading if using the phone app. Delta waves, shelves and drops (Sugar Surfing patterns) can be seen with both screens, but more can be done with the data using the Dexcom phone app. So, advantage Dexcom for the ability to drill down on data in real time compared to the Libre. Nevertheless, I was still able to pivot both directions, and wait for the drop using the Libre.

Event markers are easier to see on the Libre but their exact location in time is not easy to determine compared to the Dexcom phone app. There are no visible event markers on the standard Dexcom receiver. Entering event information is comparable. The Libre offers a place to document long acting as well as short acting insulin even though the LA dose does not show on the screen. The Dexcom system does not differentiate insulin type when entering.

The Libre has reminder alarms only when you tell it to do so. They are loud enough to be heard. Whether they will awaken you from sleep depends on other factors. The Dexcom alarms are robust too. With Dexcom, the system will alert you in response to rates of rise, fall and crossing upper and lower alert thresholds. These can all be disabled except for the critical low alert (55 mg/dL). The Libre does not notify you of anything unless you set a reminder alarm. They might by 15 minutes (following up on a low) or 1 and 2 hours (to follow up on a meal or correction dose).

As an experienced Sugar Surfer, I already knew certain physical and mental cues of dropping and rising blood sugar which naturally prompt me to glance at the receiver, phone or reader. I also am highly familiar with my unique glycemic patterns to certain meals and times of the day when I tend to have slow drifts up or down. This experience made the Libre easier to Surf with.

Accuracy of the Libre was as good as the Dexcom, maybe better. This was as compared to fingerstick readings. There were some instances when Dex was closer to the meter, but overall, I would say that the Libre is in no way inferior to the Dexcom as far as accuracy goes.

Cost is lower for the Libre compared to the Dexcom. This is not an opinion, it’s just a fact. But costs vary based on many factors so consider this a variable advantage. I paid $40 USD for a sensor. The Libre reader and a single sensor were offered as part of a promotion to existing Dexcom users, so I paid nothing for them. I self-funded the second sensor mentioned above.

The Libre reader is light, just a few ounces. It does not have a carrying case like the Dexcom receiver but it’s noteworthy that the smart Phone app has replaced the stand-alone Dexcom receiver for many. The Dexcom transmitter combined with a phone app does not increase the items to keep up with, aside from the phone itself. The Libre reader does not need to be near the user until of course a reading is required. Then you need to go get it unless you carry it on your person. A loose meter sized reader is easier to misplace or fall between the sofa cushions. You might want to put a tile on it.

The Libre reader is also a meter as I mentioned. It uses Freestyle Neo strips. These require more blood compared to a Freestyle Lite strip. I rarely used it.

The two greatest disparities to me are the lack of threshold alarms and the lack of a share feature. Both are strengths of the Dexcom and its app. There is a third-party appliance which can convert the Libre sensor into a Bluetooth device with a share-style app. I have not used this so have no comments about that. Parents using Share with kids must invest in a second smartphone to combine with their system, which is not inexpensive.

For now, parents or care givers who wish to have a Share feature will be disappointed. On the other hand, older users who don’t want to have the annoyance of unsolicited BG alerts going off in public may prefer the Libre. At least they get to choose when to check a reading. Those persons with a good working awareness of their own low blood sugar signs and symptoms definitely benefit. A good working sense of hypo awareness during sleep is important too. Many persons with diabetes still retain this ability despite what some may think based on what they see online. Many Sugar Surfers also report improved glycemic awareness after several months of sensor use.

I would endorse the Libre for use in teens and adults with intact hypoglycemia awareness who want a keep a low profile with their diabetes. There is an externalization of diabetes due to waving the reader within an inch or two of the sensor, but most onlookers would never really pay much attention to that. The sensor transmits well through layered clothing and coats too. It requires a proximity of 1-2 inches from the sensor to capture data. Most people think my Dexcom receiver is a tiny phone or pager. I also have an Apple Watch with the Dexcom readout on it for quick glances. The Libre reader counts average glances. I looked about 19 times daily. That seems to have fallen off in the second 10-day trial I’m on now.

The touch screen on the Libre reader has a different sensitivity than your smart phone or tablet. You will have to experiment with the amount of pressure to apply over buttons. Interestingly, the starting default amount for carbs logged is 15 grams, but you can scroll down as needed. As mentioned earlier, you can also insert your long acting insulin dose separately from your rapid acting insulin. This is not an option I can see on the Dexcom app; insulin is insulin there. Unfortunately, I find less than 10% of CGM users actively use or take advantage of event markers.

While I cannot scroll to exact values on the single trend line displayed on the Libre reader, it is possible to see delta waves, drops and shelves in the last 8 hours displayed. I can’t go back any further without going into the logbook function on the reader. These are vital Sugar Surfing patterns which are essential to be able to detect. Waiting for the bend can be done sooner than with a Dexcom.

One potential advantage of Libre is the ability to collect a new glucose value every minute. This was something I really came to enjoy with the Abbott Navigator. To take advantage of this, you must actively check BG often. The only risk to that is giving the outward appearance of brushing off shoulder dandruff every minute or two.

Let this table serve as a summary of my observations

My conclusion is that Sugar Surfing and the Abbott Libre Freestyle are very compatible. There are certain limitations as outlined above. Parents of children may not like the lack of real time data sharing, but some teens might prefer it. Cost favors the Libre along with ease of insertion. I cannot make any definitive statements about adhesive integrity with heavy sweating, but the Libre unit adhered well for the entire 10 days I wore it. Finally, as many Dex users re-use their sensors after 7 days, that is not possible to do with the Libre. The reader will not recognize an old sensor. If there is an easy way to do this, it's not something I'm aware of.

In closing, Sugar Surfing will always be a practicable skill. It is not about how our BG data are collected, but how the data we collect are interpreted and used for dynamic decision making.

Disclaimer: I have no conflicts of interest with either device producer. I am on no speakers’ bureaus, hold no company stock or other interests. The above comments are completely non-scientific and represent one user’s perspective and experience. Any errors in my analysis or assessment are mine and mine alone.