mySentry Trial: Wearing the Sensor

Last post in this series: mySentry Trial: Starting Up

I wore the pump for about a week before starting on a sensor.  That time was used to become familiar with the basics of delivering insulin with a pump that was brand new to me.  My sensor training went great, and without any trouble I was up and running.

I own a Dexcom SEVEN+ system (a different brand of CGM) and decided that I wanted to wear both devices to get a feel for how they compare.  I didn’t do any scientific comparisons, I didn’t keep any detailed records, nothing fancy.  Just anecdotal observations.

Medtronic and Dexcom CGM Transmitter

The transmitter from each system

The first low I had while wearing both systems just about rocked my socks off.  Lows are often unsettling, especially when right in the middle of something, and on top of that I had both devices buzzing and beeping at me.  It was completely overwhelming, and I questioned whether I’d continue to wear them both.

But I did continue, and I discovered something very interesting.  When one system was off (not matching up to actual blood sugar numbers), they were both off.  So maybe perceived inaccuracies between brands of CGM technology actually come right back to something weird happening in the wearer’s interstitial fluid rather than either of the devices being wrong.  That was a real eye-opener for me.

MedT Sensor Introducer needle and device

Huge needle

Inserting the Medtronic CGM sensor was surprisingly painless for me.   During the course of twenty-plus sensors, there wasn’t a single one that hurt.  This surprised me because the needle (and the sensor, for that matter) are pretty big.

Actually, the needle is huge.

In this picture, you see the sensor and needle loaded into the Sen-serter, a spring-loaded sensor insertion device.  For the record, I am a fan of spring-loaded insertion devices.  I like that they help me with a quick insertion, something I’ve always had trouble with doing manually.

Again, I want to say that, even though the needle is the largest I’ve seen/used, not a single insertion hurt.  Not even a little bit.  I had one that bled like crazy, but even that was pain-free.

The process after insertion was slightly confusing though.  There is a 5-minute “wetting” period after insertion.  What that means is that you have to wait for at least 5-minutes before plugging in the transmitter.   Once plugged in, the clamshell is supposed to show a green light (that part is kind of cool. It seems the light is buried way inside, but still shows through the clamshell skin).

There was a couple of times where I didn’t get the green light, and I wasn’t sure why.  I would disconnect the transmitter and try again, and then it seemed to work fine.

Calibration is also a bit harder (the system is less forgiving of blood sugar on the move).  Jeff talks a lot about calibrating in his CGM post (a wealth of tips and knowledge), and something that Wil talks often about too.  The post I’ve linked to for Wil is quite old, and many things have changed since, but still offers a lot of wisdom around calibration.

CGM Integration

The CGM integration into the Medtronic pump felt very sophisticated compared to what I was used to with the Dexcom system.  I could dig deeper into the historical data, I could see the amount of time left on the sensor, and I could see when the next calibration was due.

Queued data rocks.  If the clamshell transmitter loses connection to the pump, it can store up to 40-minutes of CGM information.  Once the communication is re-established, it back-fills all of that information into the pump.  This was great for when I was taking a shower, or just after basketball when my pump is in my locker and I’m cleaning up.  I had very few gaps in my CGM graphs.

Another thing I really enjoyed was the ability to silence alerts for a set period of time.  I used this when I knew my CGM wasn’t tracking very well and didn’t want to be pestered by any of the alerts.  I could tell it to be quiet for whatever period of time I wanted, and it left me completely alone.

Wearing the System

Physically wearing the system proved to be more troublesome.  Especially during basketball.  I made a little video to explain.

I’ve never used more extra tape and crazy solutions to keep a CGM sensor in place.  Ooh, wait.  That’s a lie. I once used toupee glue to keep my Navigator sensors on.  That probably deserves its own post…

These sensors are approved for three days, which feels really, really short.  That being said, there are times where my Dexcom sensor itches so bad by day 5 or 6 that I’m ready for it to be gone.

And yes, I know that people restart their sensors.  Officially I did no such thing.  Unofficially?  I couldn’t keep the damn things on long enough to do it.  One or two basketball sessions and they were toast (clamshell flop).

Another thing I had trouble with is the holes they left in me.  I don’t know if it’s due to the size of the sensor, or the clamshell flopping, or something else, but these things seemed to leave much bigger (and more irritated) holes in my stomach.  In fact, the holes took longer to heal than the three days each sensor is approved for use.   I know my stomach is no masterpiece, but it looked like it had been shot with a shotgun by the time I had used a couple months worth of sensors.

Last Two Small Irritations

I once got a CGM alert on the last screen of programming a meal bolus.  After confirming the CGM alert, I had to start the whole bolus programming sequence over again.  I know it’s not a big deal, but it bothered me enough to make a note of it.

In that same vein, when I got a CGM alert at night I would turn on the back-light to see what it was.  After acknowledging the alert, the back-light turns off.  I’d have to turn the backlight back on to program my correction bolus, or set a temporary rate, or whatever action needed doing.  Again, a very small thing in the big picture, but it bothered me.

Last Two Large Concerns

The CGM alarms on the pump are way too quiet.  Dangerously quiet.  Can’t hear them at night quiet.  This was one big concern that I heard from many readers.   I didn’t hook up the MySentry device for a few days after starting the CGM, and many (most?) of the pump alarms without MySentry watching over them went unnoticed.

The last concern I have is all about the weak signal.

Weak signal, weak signal, weak signal, weak signal.  All the time, weak signal.

With the transmitter on one side of my body, and the pump on the other side, weak signal.  Talk about feeling fat.  Holy crap.  Feeling fat AND having a device beep at you all day to remind you of how fat you are. I’m not a fan.

I have never had to adjust my life to a diabetes device more than when I was wearing this system.

In my years of pumping I have found a “sweet spot” on my belt for my insulin pump.  It’s become a part of my movements to keep that sweet spot out of harms way.  When I get in the car and put my seatbelt on, the sweet spot is safe.  When I am navigating tight spaces, I’m subconsciously aware of that sweet spot and keep it out of the way.

I had to change where I put my pump to accommodate the weak transmission of information between the transmitter and pump.  It caused major disruption for me.  Remember how I broke the belt clip in the last post?  I wasn’t wearing my pump in the sweet spot because the transmitter couldn’t talk to it.

I should not have to adjust my lifestyle to accommodate a diabetes device.

When I play basketball there is one place where I feel my pump is safe.  I wear it in a pouch on an elastic band that goes around my waist, and I position it specifically where I do because it is comfortable and safe. I got so many weak signal alarms during basketball that I had to use the “silence” feature I mentioned above.  Sometimes the pump would be less than 18-inches away from the transmitter and still couldn’t communicate.

It made me feel so fat.  Like I needed a satellite orbiting my stomach in order to relay information back and forth.

Final Thoughts & More to Come

I still have a lot more left to say on my trial.  This post is, by far, the most critical and complaint-filled section of my review as a whole.

It sounds like I hated the system.  Which I didn’t.  There were certain aspects of the system that gave me a lot of trouble, but overall, I still liked the system.  Stick with me, and I’ll cover those in detail in the next post or two.

Next post in this series: mySentry Trial: The mySentry Unit


I received all of the pump supplies, components, and training from Medtronic, free of charge.  I was not asked to write or say anything about my experience, I was not given any limits around anything I did write or say.  I did not receive any compensation other than the opportunity to try their products.

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15 thoughts on “mySentry Trial: Wearing the Sensor

  1. I’ve been using the Medtronic pumps, with Real-Time CGM, since February 2008, and am satisfied with both the pump and its CGM. I am, albeit, slender, which (according to my endo) is why I can wear a sensor/transmitter on my upper buttocks and my pump at my side (of course, the same side as the sensor/transmitter is on.) She said that if I were heavyset, there would be a communications problem (i;e., weak signal.) I keep my alarms set to vibrate. I do agree that the alarm that sounds AFTER you haven’t responded to the vibration is way too soft. I usually end up eventually hearing it, when I push off the covers or some such thing. Calibrating is something I’ve integrated into my life. I lived for so many years with nothing but my own brain, or shaking hands, to indicate to me that I was hypoglycemic, that I am willing to put up with any of the Real-Time system’s inadequacies. Life is SO much easier for me now than it was when I had no CGM. I did try the DexCom 7, but never the 7 plus, and I had too many ??? during the night. I live alone, so that wasn’t good for me!
    If I win the lottery, I’ll buy the MySentry, as it is outrageously overpriced (are you listening, Medtronic) and has a 1-year warranty. Ridiculous!

  2. very informative! cheers scott. by the way.. you certainly don’t look fat
    in your picture!
    iv actually lost a fair bit of weight recently following using diabetes uncut,
    it was long over due for me!

  3. When I was wearing Medtronic’s system, I had such mixed results with pain on the insertion. Sometimes it was painless, others it made me yelp! And, I also had a tough time with weak signals, especially when I’d wear it on my bra, aka the absolute worst place to try to silence that alarm.

    Also, I just wanted to say thanks for all of the comment love! It always makes me happy to know someone is reading, so thanks for making your presence known!

  4. Hey, great post. I have been wearing the Guardian sensor (no pump) from Medtronic for 9 months now, and i can tell you the weak signal doesn’t have much to do with your gut being in the way. i wear my device on the same side as the sensor and i can get a weak signal with 3 inches between them. This might get worse with how long it has been since the transmitter has been charged. In today’s world of wireless and batter technology this should be an easy fix – but i am assuming that since this is a regulated device all changes take a lot of time.

    I also love the device and love the data, but the user experience has a lot of room for improvement. Way too many alarams, and i don’t know about you but that whole 12 hour calibration alarm timing is a killer for me. i will forget the bedtime calibration once/twice a week and get woken up for a 4 AM calibration. Smaller needle would help too – i am not as painfree as you – but i do agree it is surprisingly how much it doesn’t hurt….i always dread the “puncture” moment.

    Again – great review, and thanks for the links to sensor calibration!

    @DiabetesJon (twitter handle)

  5. I’ve heard this about the “weak signal” errors. You can set the pump for how long it can go before sounding the alarm, the maximum being 40 minutes (which is also the longest it can queue data in the transmitter). I have mine set to the max so I don’t get those nagging alerts all the time, but I am warned when I’m losing data.

    A poorly inserted sensor also seems to cause those alerts, I believe. If the sensor can’t measure interstitial fluid, it can’t report a value, and the pump/receiver interprets the missing value as a weak signal. This is just my anecdotal theory and I could be entirely wrong.

    Did you calibrate the Dex and the Medtronic at the same times? I just got done reading the chapter on Calibrations in Wil’s book “Beyond Fingersticks”, and if you use a bad value or a value when your BG is rapidly changing, it will throw all your readings off.

    Can’t wait to read the toupee-glue story!

    • Thanks you guys!

      @Scott – I didn’t calibrate them at the same time as they were often replaced/inserted at completely different times. I did try hard to calibrate the MedT CGM when my BG wasn’t moving rapidly up or down, but that’s often easier said than done.

  6. You are so funny feeling fat with the weak signal!! But I get it! Dont feel bad, if I ever actually wear my MM sensor I get this same error often, and Im just a petite chick at 125lbs! LOL
    I have also never had pain with insertion either, I know the needle is huge, but somehow that super quick spring load is painless, a huge plus 🙂

  7. It does seem like they should have a longer range. You don’t seem to be getting all the errors that Wil had – that’s good news! I’ll be interested to keep reading about your experiences.