Continuous Glucose Monitor (CGM) Graph

Continuous Glucose Monitor: Dexcom vs Medtronic

I have used the Medtronic 530G insulin pump with Enlite CGM sensors for 3 years. I recently tried the Dexcom G4 Platinum continuous glucose monitor for a week.

There are things I like about both, and things I dislike about both continuous glucose monitors. I will not get into technical differences, just observations.

Full disclosure: I have used an insulin pump since 1994, and have used only Medtronic pumps since they released the 508 pump in 1999. I was an early adopter of the Paradigm in 2006, Medtronic’s first integrated pump and Continuous Glucose Monitor.

Here, I am only reviewing the 530G with Enlite sensor and Dexcom G4 Platinum for continuous glucose monitoring.

Medtronic 530G System:

The Medtronic 530G System is an insulin pump with integrated Continuous Glucose Monitor built-in. It uses the Enlite sensor.
I use the Minimed Connect option (a separate key chain device) to send data from the pump to my iPhone. I like the Medtronic Minimed 530G Continuous Glucose MonitorConnect application because it is brighter, and clearer, than the on-pump display. It is visible in both bright and dark lighting.

I like that the 530G is one integrated device for pump and CGM.  I am not using the pump for insulin delivery at this time, so I have to set my basal rates to 0, disable auto-off, and plug the reservoir hole with a cap from an infusion set with the tube cut off.

I get comments from people thinking I am wearing a pager, as it is not very stylish nor discrete clipped to my belt.

The pump reads data from the sensor, but the working distance between them is only about 4 feet before the signal is lost.  It is also a problem if you lay on the side that the sensor is on. The signal will be lost and it will generate alarms to let you know.

The alarms are annoying at night, waking you and your partner. They are persistent, which I guess is good on a medical device, but I wish I could turn some off. The alarm sound is one that you get used to, and I find that I often do not hear it and it annoys others.

You can change the alarm to vibrate, but then it vibrates every time you press a button as well as when it alarms. The batteries wear out in about 3 days with vibrate on.

The Carelink cloud software is difficult to upload to, and if you upgrade to a new computer, browser, or operating system, well… good luck. The online charts are difficult to read, and many useful charts are only on the professional edition doctors use. Medtronic added some of the doctor reports to their site recently, but it is hard to figure out which ones to use.

Dexcom G4 Platinum Continuous Glucose Monitor:

The Dexcom also has an iPhone app, but the Share feature was not included on the clinical device I tested. Dexcom G4 Platinum Continuous Glucose MonitorAs such, I cannot really compare the two. Not needing the pump features at this time, I like the smaller size of the Dexcom receiver.

The sensor is quite large compared to the Enlite. I wore it on my arm, and it was not discrete. I also found it was more uncomfortable to wear than the Enlite. It does read up to 20 feet away, which is nice.

Alarms on the Dexcom are strong and simple. They go off, and when you acknowledge them it is quiet for a good amount of time. The vibrate is strong, and I sleep with it in my pillow case to not wake my wife. The battery lasted over a week on vibrate.

The Dexcom Clarity site is nice. You do have to figure out what drivers to install, and despite them not telling you so, you must reboot your computer before you can upload data. The charts are clear, they give you an estimated A1C after 14 days worth of data, and give you clear trends.

Continuous Glucose Monitor Winner:

Neither, really.

I saw no real difference in accuracy between readings with the Medtronic CGM and the Dexcom after they stabilized. The Enlite becomes accurate after 2 or 3 calibrations, and the Dexcom takes about 2 days before it is stable.

The first two calibrations of the Medtronic CGM should be done 2 hours apart, but you can shorten it to 15-20 minutes apart and the sensor will stabilize. The Dexcom allows 2 consecutive calibration readings, and then you do not calibrate for 12 hours.

The Medtronic likes calibrations.  Although you only have to do 1 test every 12 hours, it does not hurt to calibrate more often. The Medtronic 530G auto syncs with the Contour Next blood glucose monitor, which simplifies things. The Dexcom becomes less sensitive with more calibrations, unless you follow specific recalibration requirements.

Once I figured out when it was ok to re-calibrate, the Dexcom adjusted to the new setting immediately. The Enlite will complain about  calibration errors if an input value is off from what the sensor reads by more than about 40 points. Getting the Medtronic back in sync is useless at that point.

Support wise, Medtronic has Dexcom beat hands down. You can call Medtronic and talk to a person who can answer questions, you can order a device, and the process of getting a replacement device takes very little effort.

My experience trying to order the Dexcom CGM, however, was painful. I filled out a web form,  and waited a week for someone to call me back. The guy who called simply filled out the web form information and said he would pass it on to “sales.” When I finally heard from sales, they passed me on to a distributor who will have to call me “sometime next week, probably.” I have never had this problem with Medtronic.

Not needing insulin delivery, I lean towards the Dexcom at the moment. When I go back to insulin delivery with the pump, I will lean towards the Medtronic. I especially look forward to the 670G pump and CGM coming out.

For me it is like buying a car. I have one, so I do not really need to switch from the 530G, but the Dexcom continuous glucose monitor would be nice.

We will see…