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I am relatively new to CGM (using the minimed system), and started out religiously changing my sensors every three days as instructed. Then I figured out (through the help of folks on these forums!) that I could actually "trick" the CGM into another round of three days of wear by establishing "new sensor" after the three days ran out. THEN, I figured out (again with feedback from you!) that if I recharge the battery on the transmitter, and start the above process again, I can essentially use the sensor until it won't work anymore, or until my site becomes irritated. So first, thank you!

My question is, how long is too long? My last one was in for 19 days, no probs with accuracy or at the site, but I freaked and figured I should replace it. One CDE chided me last week for not changing it every 6 days at least, but I can't really say that her concern was evidence-based (nor could she) for me or anyone else. And are there any additional risks or pitfalls of longer use of a CGM sensor that you've found?

I hate most about the Minimed CGM the insertion process, so I do, admittedly, just about anything to NOT have to change it if I don't have to... (though I have found great solace in topical lidocaine cream...).


Tags: long-term, sensor, transmitter

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My CDE Encouraged me to restart my dexcom sensors "as long as they seem to be working." She said most of her dexcom patients are able to restart them for another 7 days, and a few routinely get 3 weeks from each sensor. As long as you disinfect the insertion area and generally keep the tape and such clean after, I think the risks of infection are really very minimal, even if you leave the sensors in a long time.

I've heard of people getting a full MONTH from the MM sensors... but it seems that most I've read about average 12-15 days? In any case, as long as the results you are getting seem to be accurate, I would restart it as long as you can/

I just pulled a dexcom sensor that had been on 13 days, and the only irritation I have is from repeatedly taping over the sensor site (looks like a rash from the tape).. the actual sensor tape area and insertion spot look just fine.
Same here, Sarah. I'm on the Navigator and have been encouraged to restart unless my skin is irritated or the calibrations don't seem to be accurate. I have been wearing mine for 10 days, rather than the 5 they're supposed to last, and could go longer, but I don't because my arm starts to itch after that many days and I start getting excited about the prospect of ripping the sensor off. I have sensitive, easily reddened skin. The sensor's still working fine at that point...

Tziporah, I say do whatever gives you peace of mind. I don't think there's any harm in wearing it for longer than directed.
Whatever works for you is what's best. Everyone's physiology is different. What works for you might not work for another and vice versa. As long as the accuracy is not in question, the adhesive is not creating a problem, and you aren't experiencing any discomfort, I'd just use it until something changes.
As far as insertions, when I first saw that sensor needle, I thought .."OK, that doesn't look cool". The funny thing that I still don't understand is that doing a quick-set site stings more than my sensor insertion. Makes no sense to me and I full expected it to perhaps really smart. But when I do an insertion, I just do not feel much of anything. So far, I have only done them on my sides. I'm pretty lean but I still have not had a single problem and I don't feel a thing. I do my angle fairly steep. At time. almost straight up and down....almost. I am sure thankful I don't feel anything, but still shake my head everytime I do my sensor insert,

I recently went to the Sure-T's and now, I don't feel anything there now either. Life is good for this diabetic guy. :) I am loving my MM722+CGMS set up. My bg's have never been better. My hypo are almost gone now too.
This is an interesting question and something I've been thinking about.

Is there an increased risk/level of scar tissue formation from leaving the sensor in longer? I want to avoid forming scar tissue and then end up having absorption problems later! I've noticed that at least if I leave them in 6 days, the MM sensors seem to leave bigger marks that take longer to go away than I remember the Dexcom sensors leaving.
I have only had the MM CGMS for 3 1/2 weeks,.My trainer did not discourage keeping the sensor in longer than 3 days., She even said that MM and the other CGMS systems are trying toi get the FDA to change the 72-hour ruling about insertable medical devices,remaining in to up to 7 days; and that it may happen in 2010..So I think you can wear them longer.
. I wore the first sensor for 7 days, the second for 7; the third for 6; and took off the sensor for a little "skin rest" yesterday. I will insert it again today. Sensor Insertion in my fatty parts ( hips, sides of abdomen, has not proven painful at all, but I did get one scar on the first try.and I did notice soreness ( the very first wear) at around day 6;; but it only happened Once, at the first "Scar" site, which is still a little sore.But it is relatively small scar, that healed quickly. This is a concern for me as I am African-American and do Hyper pigment from skin trauma, even a scratched mnosquito bite...
The later insertion sites show minimal scarring and are NOT sore. I guess .I am getting better at sensor insertion, the more I do it ., as threatening as that javelin-looking( inserter) thing is...
I never plan to (1) wear the CGMS 24-7, I will be taking little vacations from it from time to time.: I do not have hypo-unawareness., (2) change it at the times I do wear it ; in less than 7 days. I get good readings, with proper calibrations, through 7 days..The tape just starts peeling up around the 7th day, so I change it out.,,

God Bless,
I would love to wear my MM CGMS longer than 6 days. Generally I get a little itchy from the adhesive. Are they using something different than what they use on the quicksets? I put a dressing over it, and wonder if it must hold moisture in?!? By the 4th day, I notice the edges of the adhesive part start to unstick. By the 6th day I can take the dressing off, and the sensor and transmitter will simply fall off my skin. The last time, I used iv prep all around the insertion area, took the dressing off to air dry ever 2nd day, and it still fell off. It's getting a bit frustrating! Is anyone else having similar problems?
I agree, Mike, that often the drawback to wearing the sensor longer is the adhesive issue. First off, I use Tegaderm, and not the IV-3000 the sensor/transmitter came with. The Tegaderm is better for my skin, with better adhesion. On day 6, I remove the tape while holding the sensor and transmitter in (to avoid it coming out), remove the transmitter to charge, and when I 're-up' my sensor (sensor start as if it were a new sensor), I use a new dressing. It also seems to help me keep the sensor in by gently pressing it in a bit upon insertion, just to make sure it's really in there. I've also had variances in itchiness and adhesion depending on the site. The one I've been using lately (my hip area, around the rear pocket line on my backside) seems to not have as much itchiness for me as did my stomach or sides. Hope that helps.
Well, I can say that the dexcom sites after 13 days (haven't been able to go longer yet) look WAY better than an infusion set does after 3 days.. so I personally am not too concerned with scarring from sensor sites... at least not yet anyways.
I have noticed severe irritation and spotting on my skin after 6 days so I have decided that, even though I "can" go 6 days, I will start changing the sensors when the 3 days run out. I do not enjoy the way my stomach looks having the sensor in the full time, usually red and icky, as if I've left the insulin pump set in my skin for just as long. I just don't think my body can handle it so I would say that as long as it's OK for you you're OK. But just know that there is at least one person who needs to change more frequently.
I once had a sensor attached for about 12 days, maybe more and wanted to get longer usuage ; I think that time it was too long ...I keep in mind now, what the area looks/feels like , is it itchy , redish and take it from there . Polysporin goes on " it" , if
" it " looks " violent " after removal ...another thing , which may work differently for every one , I think .
Just be aware , how your skin re-acts and if sensor numbers are in tune with finger pokes .
This is just my opinion, but I think the reason that health officials can currently recommend extended use of the sensors is because no one has been wearing one for 10 or 20 years, so we don't have data on their long term use.

You are forming scar tissue whenever you injure the body and sensor insertion is a very mild injury. Whether or not it is enough to impact your diabetic care in the long term, remains to be seen. YMMV

The only evidence I have seen of sensors and scarring can be found at the link I attached below. They note that the scarring will affect sensor performance after about 30 days but this does not mean that the scarring begins at day 30. At about 30 days, there is enough scarring to shut down the sensor. Just because we can get 3 or 4 weeks use out of a sensor does not mean we did not leave a small scar.

I have a suspicion that history may repeat itself. In the early days of insulin pumping, some pumpers bragged about wearing pump infusion sets for double, triple or quadruple the recommended time or they kept reusing the same sites. Years later, some started complaining of decreased effectiveness of their sites, which was later attributed to scarring.

Here is an excerpt from the article:
..putting artificial material under the skin is tricky. Any
foreign object, whether it’s a glucose sensor, a breast implant, or
encapsulated islets, tends to stimulate a mild immune response that
surrounds the implant with scar tissue. This build-up of fibrous
material, called fibrosis, chokes off interaction with the surrounding
cells. In the case of a glucose sensor, it prevents accurate reading
of glucose levels.

Kenneth Ward, M.D., a JDRF-funded researcher at Legacy
Emanuel Hospital and Health Center in Portland, Ore., is investigating
ways to solve this problem. For years, he’s been implanting
glucose sensors under the skin of animals, only to see their effectiveness
fade as the weeks go by.

“We’ve found the devices work pretty well for about 30 days,
and then you see a drop-off in the accuracy of the sensor,” he says.
“There’s what we call a “foreign body capsule” that surrounds the
implant and is made mostly out of collagen. It can get pretty dense,
and the glucose and oxygen can’t reach the sensor fast enough, and
what does get there is in very small amounts.”

This blockage reduces the sensitivity of the sensor and introduces
a lag time in monitoring the body’s true glucose levels. Unless the
blockage is prevented, implantable sensors will be of little use to an
artificial pancreas.
I was told by the Medtronic CGM sales rep that scar tissue won't build up with the CGM because it's not infusing anything the way the insulin pump cannulla is. I'm currently having a sensor error on my little one's CGM and trying to figure it out so it will stop beeping and she can go to sleep! Trying to see if there are threads that may answer my question while I wait on the phone for Medtronic.





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