My New Friend Dexcom

Hanging out with the ski patrol.

Goofing around in our vintage ski outfits.


4/23/06: Interesting Phenomenon

Extra extra, read all about it… Continuous glucose monitors and "My New Friend Dexcom" blog are national news! The Washington Post just published an article about sensors and I was given the last word about the realities of this new technology. Thank you Justin Gillis for your thorough research and articulate writing about continuous glucose monitors.

Fun and Interesting Realizations
We waited out the snow storm (from my last posting) and had an epic day of skiing at Lake Tahoe. The Northstar resort received 3 feet of fresh powder and Decom and I spent most of our time skiing through the trees on the backside of the mountain. I didn't adjust my pump's basal rate, but did eat 30 grams of carbs to prevent a low. I kept my receiver in my ski pants' pocket and checked it periodically. The skiing was amazing (powder flying with each turn), but it took an increased amount of effort to ski down each run. After 4 hours of thigh burning intensity, we called it a day and headed home. Dexcom's 9 hour graph showed a slow and steady downward trend throughout my day on the slopes. I didn't go low that day, but analyzing the graph told me that I would have needed more carbs if I chose to keep skiing that day at the same intensity.

After using the Dexcom sensor for a few weeks, I've noticed something interesting in the morning. An hour or so after breakfast, my BG soars to the mid to upper 200's and eventually falls to my target of 120. The first few times I experienced this, I did a finger stick test, which confirmed the Dexcom reading. I then thought about correcting with more insulin, but my Cozmo's Insulin on Board screen showed I had 3 or more units still active and didn't advise a bolus. It was a good thing I didn't correct, since my BG started to decrease about 30 minutes later.

After some experimenting, I've found that no matter what I eat for breakfast (oatmeal, cereal, whole wheat toast, scones, waffles), the morning spike still occurs. I've also found that if I add espresso to the meal, my numbers can reach above 300 and then come down. I thought about an explanation for this and concluded that in the morning I must have a higher concentration of hormones still lingering from my Dawn Phenomenon (early AM surge of insulin resistance causing hormones that help my body prepare for the day). I'm a little concerned that this morning spike is affecting my risk for long term diabetes-related complications. Since more insulin and changing my food choices won't correct the problem, I'm planning to talk to my doctor about trying Symlin, the new hormone that helps lower post-meal BG's. Although, I'm not excited that to take Symlin means giving another shot before meals and I've heard there's some nausea for the first few weeks/months.

Weird Phenomenon
So far, I've had a very positive experience with my Dexcom. However, I'm finding that certain conditions and situations cause "weird" things to happen with the sensor. First, my heart rate monitor does cause some interference between the transmitter and receiver. I've realized that while wearing my heart rate monitor, I must point the receiver directly at the transmitter/sensor and the distance between the units can't be more than 2 feet. Second, intense prolonged anaerobic exercise causes the transmitter to inaccurately read "HIGH" which means a BG value of above 400. This has happened a few times while running and swimming.

If I were Dexcom, I would explore how lactate, epinephrine, norepinephrine, growth hormone, cortisol, and glucagon (hormones released in high concentrations after intense anaerobic efforts) affect the accuracy of the sensor. I realize that everyone wont' be using their sensor at the same intensity that I do, but I think it's important to report my findings. Last, occasionally, the receiver will ask me for random calibrations, outside of the normal 12 hour schedule. After I calibrate, the receiver asks for another calibration a few minutes later. This happened a few days ago and I burned through 15 test strips in one day for calibrations. I'm going to call customer service to troubleshoot the idea tomorrow.

Redesign the Belt Clip Now
The Dexcom data has been wonderful and insightful. However, in order to get continual readings, the receiver must be next to the sensor at all times (day, night, exercise, shower, bed, etc) and the Dexcom belt clip isn't versatile enough to do this. In fact, on the way home from Tahoe, I almost lost the receiver due to the clip. I had the receiver clipped to my ski pants and stopped to grab a coffee to go. While I was pulling away, a stranger knocked on my window and asked "Is this your cell phone?" holding my Dexcom receiver. Here are my complaints about the clip:

  • The plastic clip does not hold well on anything but a belt. The case's high center of gravity makes the receiver flop over when worn with loose pants/shorts, workout wear, boxers, and pajamas.
  • The clip must be worn directly on my side or the receiver will dig into my stomach, sensor, or infusion set (ouch!) if I bend over. This is another center of gravity issue.

I have paid $825 for the Dexcom system so far with an expected additional monthly cost of $175, so I expect a clip (or multiple clips) that will be functional when I'm working, exercising, or lounging around in my pajamas.

In Conclusion

  • Dexcom helped me discover a post breakfast BG spike.
  • Intense anaerobic exercise interferes with my Dexcom's sensor.
  • I'm waiting for a new belt clip (and software).

Next time, I plan to compare and contrast current continuous glucose sensors. Thank you very much for all your questions, comments, and support.


I do not work for nor am I compensated by Dexcom in any way. I'm writing this story because I think continuous glucose technology is interesting and exciting. Also, I am not a health care professional and do not give medical advice. I will share my experiences, but please check with your health care team before making any changes to your diabetes or health management.