Famous "?" error whilst doing sport!

Hi Folks,
another question…hope you can help out!!
Every time I do sport, cycling or jogging etc., the famous “???” error pops-up and only returns to a normal reading after I’ve long stopped exercising. So actually this real-time monitoring doesn’t seem to work that well or bogs down under certain circumstances.(Basically when I really need it) That’s one of the reasons I’m interested the CGM system is to keep a constant watch over my BG whilst doing different activities.

Has anybody experienced the same inconveniency??

Are there any counter measures one can take to receive a continuous read-out while doing sport?

Appreciate any tips.
Thanks, Martin.

sorry to hear about your issues. I’ve had a lot of success working out with the Dex and only a few issues. The times I got ??? were when I was swimming with the sensor exposed to the water and I think after an hour of exposure the connections got wet.

If it helps, I have been putting my sensor on my rear under my shorts for the last four times or so and it seems to work really well. You might want to ping your local Dex rep as well to get some advice.

I’ve only been using the Dexcom for a month or so and have only had the ??? pop up twice. The first time it only lasted for about 5 minutes. The second time was for several hours and happened after running a 5K race. It was working fine throughout the race and all the way home but went to ??? while in the shower. My first inclination was that it was a problem with moisture but I’ve had the sensor/transmitter totally submerged in a pool without a problem. An older post here mentioned that being dehydrated could possibly lead to the ???. That seems like a distinct possibility in my case as I’m quite sure I was dehydrated after the race. I always have run 5K and 10K without any fluids and have only bothered with something during a half marathon.

I’ve only gotten the ??? after showering and the sensor wasn’t in place tight enough so it got some moisture in it. It might be from sweating?

I’ve attributed the ??? to dehydration as it happens to me periodically at night while sleeping. Drinking a glass of water before bedtime has eliminated this problem. When I insert a new sensor and I forget to do this, typically I get the ???.

good point. hearing two clicks when attaching the transmitter to the base is ESSENTIAL!

Hey Joker,



I’ve had this happen a few times. Usually, it’s a combination of a sensor with poor accuracy combined with a workout that causes my BG to change rapidly. The Dex just can’t seem to keep up and just plain wigs out.



It happened with 3 sensors in a row that I placed on my outer thigh. In the past, the outer thigh had been a really good site for me, and my sensors seemed to last a lot longer and have improved accuracy over the lifetme. Lately though, I noticed that after a week, the performance of the sensor would deteriorate to the point where I was getting lot’s of ??? while running. I’d replace the sensor and notice that the old sensor wire seemed a bit more beat up than usual.



So, I think it was the action of my contracting thigh muscles working against the sensor wire while I was running. Over time, the wire just could not hold up to the wear and tear causing the performance to nosedive after a week.

I’ve gone back to wearing the sensor on my abs and I haven’t had a problem since making the switch.

Hi FHS, I think your correct about the position of the sensor. Just finished another one and it worked fine all through the seven days. It was placed in the abdo, but in an area with a larger fat layer.
Another thing I noticed after removing the last sensor, was moisture or some sort of fluids between the 2 contact pins between the sensor & transmitter although it was securely fitted and clicked in twice. Could be caused when sweating a lot during sport.
Have since then used a larger “breathing” plaster to hold secure in place.
Seems like that helped a lot.
Will carry on monitoring.
See Ya!

Glad to hear that Joker. I did notice that I sometimes get moisture buildup under the transmitter if the sensor is in longer than 7 days. It does seem to affect the performance but it doesn’t always produce ???s.

Take care!