Any Runners using a CGMS?

For the first time since college I started getting semi-serious about distance running last summer. Rather than just plodding along 2 - 3 miles, I started imagining that I could run 10K’s, maybe even 1/2 marathons, or ??

As I started dealing with BG during longer runs I realized a pump might make things easier. So this year I went on the pump. Then 2 months later I got a CGMS. It took me a while to get comfortable and adjusted to everything, so I lost some of my fitness, but now I"m running regularly and loving it. Hoping to do my first 10K this October and my first 1/2 marathon next June.

I’m wondering if any other runners are using a CGMS and if so, does it work well inserting it in the thigh? I’m concerned that the muscle movement during running could decrease the accuracy.


Hey Ken, I don’t have a CGMS, but am a fellow runner/plodder. I’ve run in a handful of 5K’s, and am training for a couple of 1/2 marathons…one in November, and another in December. Will be doing a 10K in September as well. So just wanted you to know you’re not the only crazy, 40ish, pumping, diabetic with delusions of 1/2 marathon glory :slight_smile: Good luck with your training, and I’ll be interested to hear how the CGMS helps!

Hi Ken: I’m a runner, and I’ve been running with the CGMS (Dexcom) since February now. I haven’t tried the thigh, but I have put the sensor on my abdomen and also on my upper butt cheek. The upper butt cheek works best in that there’s not much movement there. Abdomen was OK, but I found a little more movement there. Also, I got more wear time on the upper butt cheek. Good luck with your running. I had a bad low while running last summer so CGMS gives you a lot of freedom to treat the tread…especially with the longer runs. Peter

Hey, Ken. I used the Dexcom and had it while training for the L.A. Marathon last spring. I’m now training for the Long Beach half-marathon.

I use the CGMS in my abdomen, but I find it unreliable during strenous activitiy. It was not good at catching lows, which I felt LONG before the monitor caught up. I think it’s a case of the monitor not being able to stay on top of fast changes in glucose levels. I can speak at least on the 3-day sensor and it may just be my physiology. I just upgraded to the 7-day and it may be more useful. I’ll report back.

Right now, I rely on fingersticks every 30 minutes while I run. Since I carry my water bottle on a belt the extra weight of the testing kit is really nothing.


I just got my cgms and I am back to running again. I like it so far. I have only had the cgms for 2 weeks but I could see trends better and I could adjust my basal rate better. I trained last year ( started in Jan ) to run a 1/2 marathon. My a1c was very poor 9. During the race my sugars jumped to 450 and I didn’t know it until I felt it. Now with the cgms I could see trends. I did finish the race but I was hurting.

Wow John, 450 can’t feel good during a run. Your having completed it anyway says a lot for you self determination.

The initial reason I went on the pump was because I figured I could achieve better BG control on long runs. Now with the CGMS, I’m thinking near-perfect BG should be possible. Here’s one persons experience with near-perfect BG during a 1/2 marathon:

A Runner’s Training Diary

Hey Ken,

That was a very informative article. Thanks,


I had an odd experience with my CGM today, although the oddness was really in me.

I run after lunch every other day and normally reduce my lunchtime bolus a full unit to account for the run - generally 3 miles. As I walk to the gym to change it is not unusual for my CGM alarm to sound off indicating a high. It did that today, but when I looked at it it was actually alarming for a low.

I decided that it was full of crap. It had been ‘noisy’ all night. Stupidly I left my BG monitor at the office so couldn’t take a finger stick to confirm. In any case, I didn’t FEEL low. At least I didn’t THINK I did. The low alarm kept me wondering and I started to feel some minor tingling but the kind you get when you’re either high or low. I wondered if the CGM could induce a ‘psychosomatic low’?

Started the run - felt great - good form, nice pace, strong rhythm - wondering all the time, “am I going low or is the CGM full of it?” After a mile I felt it. It was me that was full of crap.

I ended the run, walked back to the gym, showered and changed, got to the office and did a finger stick. I was indeed low. Not as low as the CGM said, but too low to finish the run. At least I’d smartened up by then.

I finally figured out that the mid-morning correction bolus I’d taken earlier was probably the culprit - even though the bolus wizard should have accounted for it.

The lesson learned is to keep my BG monitor handy. There’s a reason not to fully trust the CGM for treatment decisions, it’s often off by 20 or more points - the source of my distrust. But since I have it I shouldn’t dismiss it. It was showing me a trend even if ti wasn’t right on the mark. With or without the BG monitor or CGM, it’s important to listen to your body.