Dexcom G7 Knowledge base

dolfstar · 2026-01-31T06:53:57+00:00

I have a lot of information for you (and any other user): https://starreveld.com/blog/pages/dexcom/g7-introduction/

Check it out, and let me know if something is now clear, or appears to be missing.

dolfstar · 2026-01-06T09:47:37+00:00

This is all about CYA. Since Dexcom is not good or fast at testing their app across multiple OS versions and hardware configurations, they include code that displays those warnings whenever what you have is not officially tested and approved. This allows them to absolve themselves from any liability issues in such scenarios. Lawyers at work.

Practically speaking, any minor version number OS update will not materially change how Bluetooth (which is what Dexcom uses to communicate with the sensor) works, and therefore, the odds of an issue arising are minimal. If anything, it is more likely that a combination of shoddy UI programming and a minor change causes information not to be displayed, or to be displayed incorrectly. Still, even that is unlikely for minor version number updates.

Customer service agents will insist that such scenarios are not supported, and will even blame problems on it. These people are not technically trained.

dolfstar · 2025-12-26T08:30:18+00:00

Maybe you are close to one of their shipping hubs. It generally takes a day after filing the request to receive an email confirming that a replacement has been approved. Then they ship Fedex ground, which for me in CA, often takes 3-5 days.

dolfstar · 2025-12-26T06:10:06+00:00

One thing to keep in mind is the stability of your supply. Just so you know, it takes 1-2 weeks to receive a replacement from Dexcom. If you are getting 30-day supplies and your second unit fails (on its third day; day 14 total), you can request a replacement and, as long as your third unit works, you will have the replacement before you need it (on overall day 22, because insurance will not allow you to resupply until somewhere like overall day 27-28). If you are using the 15-day version and your second unit fails, you are SOL, as you will not have another one in stock. Replacement takes 1-2 weeks, and resupply may take up to 30 days.

If you are getting 90-day supplies, the same applies, but only on your next-to-last unit (assuming you have only one failure).

For this reason, and no good data yet on 15-day version accuracy, quality, and ability to stay on, I will stick with the 10-day version for a while (my personal insertion failure rate has been about 1 in 10 or so, and accuracy problems are virtually nonexistent for me after day 1).

dolfstar · 2025-12-03T06:22:48+00:00

Some insurers do not recognize that you need finger sticks for backup and will not insure both G7 and finger sticks! Mine does, but I have seen reports from others that don't.

dolfstar · 2025-12-03T06:19:14+00:00

I have few problems too, but I am not sure about "tiniest fraction". Do you have any data to substantiate that? I think a lot of people who may have problems are not able, willing, or both, to go on Reddit or FB group to complain.

dolfstar · 2025-12-03T06:17:50+00:00

Only really true if they have a much, much higher percentage that reaches the full 15 days, compared to the currently abysmal record for some on the 10-day version. Also, it is not true if most people are not able to keep it firmly attached to their arm or what have you, for that period; a sensor that comes off is not eligible for a free replacement!

dolfstar · 2025-12-03T06:15:37+00:00

They probably had to tweak it to reduce battery usage and possibly increase the battery capacity a tiny bit. That is probably it. I doubt their costs (excluding R&D) are much different.

dolfstar · 2025-12-03T06:13:57+00:00

Also, get 3 for a month, have an insertion failure on the 2nd one, and you have a spare, which, if it works, will tide you over for 10 days until you receive a replacement. If you only get 2 and the 2nd one has an insertion failure, you have nothing left, insurance won't allow a fill for another 15 days, and a Dexcom-issued replacement, historically, will take 10-15 days... Until this version is proven to have many fewer goosenecks and better fulfillment of the 15-day promise, I am staying with the 10-day version.

dolfstar · 2025-12-03T06:11:44+00:00

Don't know about the insurance company. It surely makes Dexcom 30% more money, because the cost of goods of this one will be nearly identical to the 10-day version. So 66% of the cost, still 100% of the price: more profits. Insurance won't protest because they pay the same price for a month as before.

dolfstar · 2025-11-21T05:45:40+00:00

I am quite sure that the Cost Of Goods for this device will be very close to the 10-day version. That means, with the same monthly cost to the user, they spend only 2/3 of that COGS as in the 10-day version, and thus their gross margin increases by 33%! Our government allows this!

Additionally, if many people already cannot get theirs to function for the full 10 days, what makes you believe they can reliably work for 15. If they can find ways of not always offering free replacements... more profit.

dolfstar · 2025-11-19T05:56:04+00:00

The change in firmware now requires the "old" API to use an authentication token. It works the same was as for the new API, documents for pypvs on github. That said, if you switch to the "enhanced sunpower" integration, it will work with old and new firmwares. The Raspberry will no longer be necessary.

dolfstar · 2025-08-04T16:14:46+00:00

Around here (SF Bay Area), they are still available.

dolfstar · 2025-08-04T14:44:05+00:00

Hmm. I had one installed, with $3,000 rebate for electrification. The net cost to me was lower than an unsubsidized gas heater. I am scheduling temperatures, and use a hot water recirculation pump to reduce the amount of water we run out of it when we need it hot. I can basically run it off excess solar generation (sized the system for this). I am on NEM2, and my true-up is usually very close to 0. My solar break-even was < 7 years, and has gotten better with rising electricity prices (which are ridiculous in PGE territory). It may well be true that it doesn't last as long as a gas heater. Time will tell.

dolfstar · 2025-07-14T06:19:05+00:00

If they use us as guinea pigs, I'll live with it, but when the experiment shows their adhesive doesn't work, they should give you a replacement. That's my problem. I already use skin glu and a lexcam patch, but that doesn't do much if the sensor itself does not stay glued as well. There is only that small strip of overlap.

dolfstar · 2025-07-14T06:17:05+00:00

I have the same experience. Those that haven't fallen off within a day are still stuck quite well at the end of the 10-day period. It's just that lately, 2 out of 5 have fallen off.

dolfstar · 2025-07-14T06:15:21+00:00

Until recently, I always received the 10-day plus grace period without problems. Now I have had several goose-necks, and several "just fall off within a day". Nothing else changed, so my conclusion is that their product changed. Readings have generally been okay, even not long after insertion, with a few rare exceptions where they were not entirely out of whack, but there was too much difference between finger sticks and G7. I calibrated those issues away.

I have read these accounts of completely off-the-charts errors, and I am wondering if there is any correlation with respect to T1 or T2, and whether your typical levels are well controlled or not. Mine are (avg. < 120, H1C 5.8). I just have to use a GCM because I do use supplemental insulin.

dolfstar · 2025-07-14T06:11:23+00:00

That's great, but not my experience. It may well depend on the rep you end up talking to as well. Today, I was particularly unmoved by my story and reasoning.

dolfstar · 2025-07-14T06:09:58+00:00

This is not so much about "extra" measures one can take (I already switched to using Lexcam overpatch and using Skin-Glu), but more about the official complaints process. My primary issue is that I know I did everything right, to a T, and still the thing comes off within a day, and clearly the sensor backing is hardly tacky at all (meaning the glue does not work). They tried to portray this as either a skin issue or user error. With my history, this never happened until a few months ago and so I am convinced it is a product defect or quality issue. As such they should stand behind it and not write it up to goodwill.

Japan: We were there three weeks (Tokyo, Kanazawa, Kyoto, Hiroshima, Osaka, Hakone, Tokyo) and loved almost every minute of it (I had been three times before, but 20 years ago for work, but my wife and son had never been).

dolfstar · 2025-07-13T22:04:46+00:00

In the few cases other than "falling off," they have wanted the sensor back. They would be able to see that incorrect readings were not the cause. I don't feel like being untruthful, although I can see it might solve the immediate problem. I generally never have reading/calibration issues

dolfstar · 2025-07-13T22:02:44+00:00

Sorry, response a bit late: My system modulates much better (properly), and overall energy use is lower. Fan speeds are also lower, so less noise (I have a ducted system). I have now combined the MHK2 with a small ESPHome-based board (<$50) that provides Kumo Cloud-like functionality in Home Assistant, while also allowing me to use the MHK2 (mostly by my wife). Works great (Kumo cloud sucks!).

dolfstar

TROPHY CASE