@daisymae
EDIT: Sorry. This turned into a short story.
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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.
Anyway.
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.