Dexcom G6 and outdoor exercise

I ride my bicycle 3 times a week for 1 hour at a fast pace. I keep my Dexcom G6 receiver in the front of my bra for easy access and so I can hear it if it alarms. It is rather hot here (Nevada) and 4 out of 5 times by the end of the ride I will look at it and it will show a sensor error/lost signal. Once I am back home and my receiver is sitting on my desk next to me, it takes about 15-30 minutes for it to reconnect. While doing this intense workout, this is one time that it is most important that it is working correctly. Could it be the heat, sweat or motion of the bicycle?


Hey @HippieNerdBabe! First of all, welcome to FUD. Lots of exercisers here. Glad to have you join us!

It is from the sweat loss. It is a very common thing with CGM. Once you get dehydrated, your body’s interstitial fluid becomes depleted, and the CGM will not work very well.

Here is some technical info, if you are interested. (Once you start asking exercise questions around here, there are a few people that get all excited and start explaining stuff. :joy: )

  • Intracellular fluid is the where most of the body’s fluid is contained. This fluid is located within the cell membrane.

  • Extracellular fluid is what surround all the cells in your body.

  • Extracellular fluid has two primary parts - the fluid component of the blood (plasma), and the interstitial fluid that surrounds all the cells.

Your CGM gets it readings from the interstitial fluid. But all the fluids are connected. If you get dehydrated, your blood plasma volume decreases (and your heart has to actually work harder during exercise!). Decreases in blood plasma will also reduce the interstitial fluid.

Here is a pic, hope it helps.

If you really want to get geeky with it, here is a good reference.

If you are interested, we can get you setup with a way of using your BG meter while riding, so the CGM issue does not present as much of a problem.

Welcome to FUD!


Any help you can give would be appreciated. Would being super hydrated prior to riding help? I moved to this part of the country a year ago and I’m still getting used to exercising in the heat.


Yes, that would help.

You can also figure out how much sweat you lose, to get an idea of how much you should be drinking while riding.

Here is a little summary on how to calculate it:


IMHO, any water helps for your cgm to give the most accurate readings. I run, and in this intense heat, I sweat terribly. My solution is to drink water all along the way to rehydrate myself. Then when I am finished with my run, I drink 48oz of water immediately. I have found that the more hydrated I am, the more accurate my sensor is.

Hope that helps some, and I hope you don’t melt in Nevada. NYC is just shy of being unbearable :sunny:


A few more things.

Have you had your sodium levels checked? How is your blood pressure?

If your sodium is not high, and your blood pressure is not high, taking salt tabs might help your hydration too. It can help your body absorb more water while exercising, and can reduce the sloshy feeling in your stomach you might get when drinking a lot of water.

If you are only drinking water, you can develop an electrolyte imbalance. The remaining electrolytes will be diluted. Once you have an electrolyte imbalance, water that you drink will not be absorbed well by the stomach.

If you are considering this, make sure you have your BP and sodium levels checked first. And if they are okay, the brand to use is SaltStick.


@Trying & @daisymae - also the same for you. Consider having your sodium and BP numbers checked and possibly taking SaltStick during the very hot months.


Thanks, @Eric. Yes, both sodium and BP are low for me, and I do have SaltStick but I frequently forget to bring it! :grimacing: I’m going to put it next to my water bottle!


I have found a wonderful trick from keeping myself from getting dehydrated :

PICKLES. Personally, my favorite are the unsweetened Gerkins. I refrigerate them and then pop them in my mouth one after the other all afternoon and with dinner (if the flavors permit :wink:.)

I highly recommend them :yum:


Thanks for this recommendation!!! I’ve started eating them, too!


This is not a fair thing to recommend because you live in the land of high quality local pickles. Many of the rest of us are only getting pickles from the grocery, and they definitely aren’t as good as New York pickles.


Are pickles a national obsession in the US? :joy:


Yes, it is true that I live in the land of supreme pickles, however, the pickles I love best are actually from the grocery store. They are the tiny Gerkin pickles that come in a very ordinary bottle and are produced my a company called B & G. They are simply marinated in salt and vinegar rien, and not only are they good for replenishing salt, but they are extremely good for Insulin Sensitivity and gutt health! A win-win of food groups :wink:


Back when I was young and ignorant in different ways than I am now, we had salt tablets that were simple pressed salt. The test to see whether to eat one while working in high heat was simple. Lick one. If the reaction was “yum” that means you need it. If the reaction was “blech, salty” then you need water instead. An intermediate “indeed, it does taste like salt” also meant it wasn’t really needed, so no reason to take it. And of course we never took salt without concurrently taking lots of water. This was all founded on the primitive belief that your body knows how much salt it needs, and you can ask it directly, if you pay attention.


A lot of these old adages have some truth behind them!

An experiment was done where people had to perform a certain amount of time on an exercise bike. The researchers then offered them different soups after they finished their exercise.

The exercisers consistently showed an unconscious preference for the saltier soups after they’d been sweating. The researchers concluded that our bodies are good at correcting salt deficiencies through dietary intake when needed.

This has been repeated a bunch of times, here is one of them. This one was basketball and jogging instead of cycling.


Welcome, @HippieNerdBabe

When it is hot and I go running, often I will lose my sensor signal after a while also.

FYI, whenever I have a question about sports and diabetes, I ask @Eric: he always knows!


FUD Exercisers and Experts:

While I don’t exercise as vigorously as the rest of you, I do seem to generate a lot of sweat …

In your collective experience, are there lower sweat areas and higher sweat areas? If you are riding a bike, for example, do your legs get dehydrated more quickly than your upper arm?

In other words, I’m wondering for any particular exercise are there better and worse sensor locations in terms of signal loss due to dehydration or is interstitial dehydration pretty uniform everywhere on your body?

Thanks for your consideration.

Stay safe … and hydrated!



I know that I am no expert exercise guru by a long shot, but perhaps this will help: I am on the 14 day FSLibre system, and the only place you can wear it is the upper arm. I wear mine on the back of my arm right below my shoulder and near my armpit. I wore it there while I was swimming and I continue to wear it there while I have started running. Two totally different exercises, but tons of sweating from both. During my exercise, I drink enormous amounts of water to keep hydrated, and when I am finished with my workout, I drink another 48oz of water before refueling with protein and carbs. I have found that with a sensor, hydration for accuracy is key. It seems to keep the interstitial fluid available and prepared to deliver the necessary info with accuracy. Hope this helps some :grin:



Thanks for those tips. I tried my upper thigh for a while, but had more problems. I have also had better success with the back inside of my upper arm.

Stay safe!



Just out of sheer curiosity, are you on the G5 or the G6? When I was using the Dexcom, there was no way that I could contort myself to insert my sensor on my arm. With the Libre, it has an auto inject and is so easy that I could do it blind-folded. no need for contortion :rofl: