Decom swimmers please help me out

i have been on the dexcom before, but not during the period where i was swimming in a long, full sized swimming pool.

i would like to go back on the dexcom as i believe it is such a helpful tool in learning about my trends, high and low alarms, and reactions to different foods.

i want to be able to bring it to the pool with me and set it on the bench near the pool. usually i get out every 1/2 hour to do a fingerstick to make certain it is safe for me to jump back into the pool and to know if i need to eat some carbs or not.

i have read on my swimming thread that there are a bunch of you swimmmers out there who use the dexcom for exactly the same reasons i would like to.

my question is this: dont you go out of range from the receiver when you are on the opposite end of the pool? dont you get those funny icons (???) until your dexcom can read your sensor properly again? how does this work for you?

SOS. all comments are appreciated. i am really looking forward to trying this out for myself.

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Would you be using the G4 or the G5? Do you plan to use only the receiver or also have the readings going to a Smartphone?

Is Medicare involved at all that would restrict your choices?

I am not swimming with a Dexcom so I hope you don’t mind me sticking my nose in.

I am on Medicare, but my endo knows his way around the BS. I currently have an expired G5 and a receiver as well as an Apple IPhone. I don’t know yet if Medicare pays for the G 5 or not, but I’m fine with the G 4 if that’s all they will cover. I’ll find out next week.


EDIT: Sorry. This turned into a short story.
= = = = = =

Are you on an “Advantage” plan or the “regular??” medicare?

(I show my ignorance - sorry)

The Advantage plans right now do not cover the Dexcom although there is a pilot program that I saw an article on where they are (I guess) beginning the process. But the (regular?) Medicare does cover the Dexcom G5 system. Medicare does not provide any coverage for the G4 system.

If having Medicare provide coverage, AFAIK, the process all goes through Dexcom directly - no distributor involved.

When using Medicare to cover the Dexcom G5 cgm, you are restricted from using a SmartPhone as your device to receive the cgm data on and are expected to use the Dexcom Receiver. If you were to ignore this restriction and use the Dexcom App on a SmartPhone anyway, it is trivial for Dexcom to be aware of this and they are required to send you a nasty-gram and/or report you to Medicare. Failure of Dexcom to do this could lead to Medicare pulling all reimbursement for everybody from Dexcom so Dexcom in this instance really has no practical choice in the matter. However were you to use the xdrip or spike application on the SmartPhone instead of the Dexcom Application then Dexcom would not necessarily be aware of your rebellion unless you choose to link those app into the Dexcom Clarity servers in which case you would like be raising the red flag you were trying to avoid.


Point being.

At the pool, you can choose to use the Dexcom Receiver to read your cgm data or a SmartPhone. (Entire above applies to this choice.) The Dexcom Receiver is not waterproof nor is it covered under the warranty for any water damage. So if using the Dexcom Receiver around the pool, if it is was me (and these receivers are expensive in the range of $500 ??), I would put it into a tightly sealed ziploc baggie or something to avoid splashes and if it fell in the water hope the baggie held it dry long enough to fish it out quickly. I would be a bit nervous but would probably feel good enough with a good ziploc protecting it. Or is using a SmartPhone, most SmartPhones (I think??) are waterproof/resistant currently or people get the Otterbox or whatever to protect them so splashes and perhaps the accidental dunk would be ok or at least not expensive.

Obviously when swimming, you would like be in and out of range. The G5 transmitter stores 3 hours of data onboard the transmitter. So when out of range, the data gets stored (every 5 minutes there is a new cgm datapoint/reading) and when the G5 transmitter (ie - you) comes back into range of the Dexcom Receiver or the SmartPhone (running the Dexcom App or the xdrip or spike app) then the G5 will do a data dump and fill in the missing gaps for all the 5 minutes.

Although with the amount of swimming you do, I really don’t think it takes you 5 minutes to do one lap. (I could be wrong but I doubt it). But the G5 only does a data synch (whether the G5 sends the data or whether the Receiver requests the data - technical discussion and not totally relevant) every 5 minutes. So, it certainly is possible that everytime it tries to synch, the timing is off and you just happen to be on the far end of the pool. As well, when the G5 transmitter (ie - you) is under water, the water acts as a natural barrier to radio frequencies. It is not exactly block it but certainly reduces the range of the transmission. The more water in the way, the less distance.

So when you hit the end of the lap lane and want to check your BG, your Receiver / Smartphone might or might not have the data ready for you to see. I would think the odds would be against you. If you sit and wait for up to five minutes, you would see the data. I doubt you want to wait that long. Maybe if you were on the lap lane on the edge of the pool and had the receiver in a chair in the middle of the lap on the edge it might be able to pick you up while you swim?

However even if you are not able to use it for the quick checks while you swim, it should at least give you a good data dump when done so you can see how your BG is going between the fingersticks.

On the other hand, if I recall, the Dexcom never worked well for you.

So potentially this is all moot if the readings are just not accurate regardless. At the end of the day, that may be the biggest issue.


I use a Dexcom, but I don’t tend to interact with it while I’m in the pool.

Your swim routines sound like they’re more aerobic and longer whereas my swims tend to be anaerobic and much shorter.

Given that my routine tends to only be about 30 minutes, I don’t bother with the Dexcom during the routine. However, it’s incredibly helpful afterward. It’s not uncommon for me to have lows awhile after a swim, and it’s nice to have the alarms.

In addition, I recently tried working out at a different gym where the water was much warmer and I wasn’t biking to the gym in advance (aerobic cancelled out anaerobic = flat line blood sugars during swim). Without the biking and with the warmer water, the spike in the pool was very pronounced. This type of change (if it ever occurred) may have been visible on your meter though using your current methodology.

I wish I could be of more help!!! Unfortunately, I don’t think I’ve used a Dexcom in the way it might be most useful to you during a swim.


thanks for your “novella.” i found it very helpful, chock full of information. i am pretty certain that i would be eligable for the G5 transmitter. i am on regular Medicare.

you have a great memory of my “Dexcom Story” with my being so thin and all. but there are so many thin athletes who wear one without a problem i thought it might be possible for me to try it out again and just use a different site (like my shoulder/arm, for instance) (my belly is not a belly, so it never worked there). also, i would get a bit crazy with it, checking it every second, anxious over the trending direction arrows.

i thought, though, that there must be some very positive things i could learn from it as they realate to my swimming. i’ve been finger pricking over 20 times a day now, and my finger-tips are so sore, so callused and damaged, it would be great to be able to just look at the receiver and know where i am at. since my swimming, my basal and ICR needs have changed so much. i do all the finger sticks to get a good, clear picture on my trends. it makes it easier to find patterns. if you’ve follwed my swimming thread, you’ll know how my insulin needs change from swim days to non-swim days. consecutive swim days change my pattern even more.

my thoughts are that i would rely upon the dex for as little as possible, but use it to help me prevent crazy lows and crashing post exercise, as well as ward off spikes from the different types of foods i am eating since i am fueling my swim. (my entire diet has changed since i began swimming and i am now including foods that i never did in the past; i have no experience with how my body reacts to them, even as experienced as i might be)

so, all that being said, i am seeing my endo next tuesday and he will hook me up for a one week trial. i want to go in with as much info as possible. and, of course, i wanted to know about how well the Dex might work for me while i am doing my laps. i remember that there was a distance issue with it in the past. that you would lose your signal if you got out of range. just wondering how other swimmers deal with this.

anyway, thanks again, thomas. very appreciated!!!


Good Luck with the trial. I hope you get accurate numbers !!!


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thanks again, thomas. i am very excited about it.

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I have found that when I shower, my numbers on the Dexcom tend to rise (inaccurately). As soon as I’m out of the shower, they fall back to normal. This may be something to keep in mind while swimming and showering. I think it may be the heat that is the problem rather than the interaction with the water though. If that’s the case, you may not have problems in the pool. In general, when my Dexcom has backloaded my blood sugar levels, heat is more likely to cause inaccurate readings than water on it’s own. Let us know how it goes!!!

I’m happy for you DM :slight_smile:! I hope everything works out well!


Katers, i never heard about this before. i could only imagine what taking a sauna would do :wink:

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I would disagree.

I do believe that you personally have not been contacted from your insurance. That does not mean others on Medicare have not.

I can also assure you that companies that do work involved with Medicare and other forms of government reimbursement are quite concerned about the potential ramification of running afoul. The potential business impact is quite large.

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One item I forgot to mention.

In terms of the 3 hr data backfill. This would of course be quite useful while swimming if the G5 Transmitter is unable to send data in real-time to the Dexcom Receiver.

However, the 3 hr data backfill does NOT work with the original Dexcom Receiver. It does however function with the new Dexcom touchscreen Receiver as well as with the Dexcom G5 Mobile App running on a Smartphone.

As you mentioned doing a trial using Dexcom equipment likely provide by your Doc, it would not be a shocker if the Doc provides you with the older non-touchscreen Dexcom Receiver. This does NOT support the 3-hr data backfill and as such, you may find it not quite as useful during swimming as otherwise it might be. I would expect to see a significant amount of data gaps in the graph.

However, there would be no reason to expect the trial to come with any restrictions on Smartphone usage even if you ultimately intend to get the Dexcom G5 cgm system via Medicare. A trial is a trial. So, you may want to run the Dexcom G5 Mobile App on your Smartphone anyway. With the G5, you are able to connect it to both a Dexcom Receiver and a Smartphone at the same time with no issue.


Please PM or continue in another conversation if you have any related questions specifically for me. I am muting this thread but would not want to miss anything from you.

I’m not a real swimmer, but I did do laps a couple times with CGM. I kept the receiver and pump with me in an aquapak, and located them close enough to the transmitter that I didn’t lose the signal and could easily glance at the CGM reading without leaving the water. Now with your sensor on your arm it might be difficult to keep the receiver close enough, but maybe you can find a way.

I’ll trade ya. I’m sure we’ll both be happier. :smile:

Dumb question, since I use nothing like it, but what about wearing an Apple watch or something? Wouldn’t it pick up the receiver signal each time you passed by, so you’d be able to keep an eye on your BG without having to get out of the pool?

not a dumb question at all. i dont have an answer to that question, but if that would work, it would be a perfect or at least a near perfect solution.

lets let Thomas answer that question b/c i have no idea.

SOS to Thomas !!

bkh, i dont understand what you mean by this. could you please elaborate? i dont understand why wearing the sensor on my arm would make a difference.

With the sensor/transmitter in my belly and the receiver in an aquapac around my waist, I had them probably within 6" or less, so the water was not interfering with the radio.

If you have the sensor on your arm, to get that kind of closeness you’d have to figure out some kind of armband or taping arrangement to hold the receiver near the sensor (in double layers of ziplocks, perhaps) in a way that wouldn’t interfere with your strokes but would enable you to look at the CGM display from time to time without dropping the receiver to the bottom of the pool.

My point is that the receiver has to be really really close to the transmitter when you’re in the water, or the radio signals won’t go through. Otherwise when you want a CGM reading you’ll have to wait out of the water for up to 5 minutes for the next CGM transmitter burst.

what exactly is a “CGM transmitter burst?”

As I understand it, the Dex transmitter doesn’t continuously send the BG information. Mostly the transmitter is not broadcasting any radio signal. Once every 5 minutes it turns on, sends the data, then the radio turns off for another 5 minutes. That brief radio transmission to send the data is what I meant by “CGM transmitter burst.” If I remember correctly, the old G4 transmitter actually would transmit the data 4 times in quick succession on 4 separate frequencies in hopes that at least one would reach the receiver without interference. I don’t know whether the G5 does any repeated tries via bluetooth or if it just sends it once. In any case, if the receiver or phone doesn’t hear the BG data from the transmitter, it will have to wait another 5 minutes for the next transmission to come around.