Does wearing the sensor >7 days increase scar tissue?

The past week I've been on a trial with Dexcom and am getting my own on Friday. Excited but still nervous about doing the insertion myself!

Anyway, I've read a lot about how long people can get their sensor to stay in and am wondering if those who wear it for weeks notice scar tissue?

And if so, how long have you been using Dex?

I would like to leave mine in longer to save money (even though after insurance the cost is probably less than I spend on coffee a week...perhaps it's time to re-think that addiction) but I'm young! I have lots of years of this left so I'm thinking about healthy tissue. Too bad I didn't consider preventitive care for wrinkles when I was 15!

Thanks for your feedback!

I don’t expect any scarring from the dex. I believe that the scarring from the pump is caused by the insulin, not the cannula.

I haven’t noticed any scars or anything and I often wear mine for 2 weeks.

Mine gets progressively itchier and I end up with scars from scratching.

I agree with Helmut, the infusion set used in pumping can cause scar tissue after 3.5 days or so, because something is being delivered into the body at the site. Nothing is delivered into the body with a CGM. No tubing, no infusion, and no scarring. I have used my Dex for two weeks, and a few days later, used the same site for an infusion set. The absorption of the insulin was normal, so there was no scar tissue present.

i canot go more than 7 days with mine. I get a lump under the skin…assume its scar tissue, but after reading the others views, maybe I am unlucky? I only wear 1 week, take a week off and then week on, etc.

I suggest you experiment and see what works for you.

good luck.

I had scarring from Minimed CGMS but not from Dex. I average about 10 days per sensor and it’s not skin issues that cause me to pull it. It’s just that it works so well that I don’t put up with a dying sensor.

I think my scarring from MInimed wasn’t the sensor itself but irritation from the adhesive causing surface irritation.


The “search” button, at the upper right corner of the web page, is your friend.

You have a number of extremely good replies already; I’ll just highlight a few specific points they have already made. First, though, let me point out that there are two different kinds of scarring to consider here: The subcutaneous damage from the actual wire, and the surface irritation from the adhesive pad. Keep the issues separate in your head, or your thinking turns into “mush”.

1. subcutaneous damage.

From what I’ve read, here and elsewhere, hardly anyone has experienced IR issues with Dexcom’s Titanium-shelled wire. (“IR” == Immune Response, allergic reactions.) YMMV, but SC damage usually occurs from infection. If you feel something itchy or hurting at the wire location, rather than the adhesive pad, pull out the Sensor immediately – you probably didn’t clean the site properly, and an infection has taken hold.

Except for this risk of infections becoming more established, fewer “holes” is better (IMO). In all cases, you want to avoid irritation from the wire moving within your SC tissue- some people can use Dexcom’s adhesive pad all by itself; and others get pretty good results by “patching” loose edges with Mastisol, or similar products.

2. IR at the skin surface (reacting to the adhesive).

Others, like me, react quickly and strongly to Dexcom’s adhesive glue at the skin surface. (I react to most infusion set glues in the same way.) So for me, it’s necessary to prevent long-term contact with Dexcom’s glue first. And, as it happens, the “fixes” which I use keep the pad stuck in place forever, preventing any wire movement too.

I use “Skin-Prep” underneath, and a pre-injection cleaning procedure which many people find… excessive. Then I add a big piece of “FlexiFix” on top, which keeps the Dexcom pad edges from becoming loose over time. Some others use FlexiFix underneath, with a “Doughnut Hole” cut out of the middle for the wire injection area.

Don’t ever let the pad edges get “nasty” and loose by more than 1/8" before fixing them – or the wire starts to move, microscopically. That causes IR, and also wrecks Sensor accuracy.

I think that Richard157 and Helmut are exactly right about the main difference between pump infusion sets and Dexcom. Lisa-C is correct that YMMV, you could turn out to be less “lucky” than average. I would recommend that FHS try some of the ways which others are using to prevent to prevent both the itching and the scratching. I had actual BLISTERS from the Dexcom pad, after only 3 days, when I last did a Sensor change without Skin-Prep underneath. (I was on an out-of-town trip.)

Like many others, I use the Dexcom for 14 days. If I ran it all the way to the end of the reagent chemicals, when it looses accuracy, I would get somewhere between 16 and 19 days – but this way, I don’t risk suffering lost accuracy (from a dying Sensor) at a dangerous or inconvenient time.

Courtney and FHS: Search for “Flexifix” first. It costs a lot ($40, IIRC), but the roll is 33 feet long- so just one roll will last for years and years. To fully cover the Dexcom pad in the “long” direction, you’ll need to buy the harder-to-find 4" width. You cut off, then trim-to-fit in the narrow direction, using a piece slightly less than 3" tall. If the FlexiFix adhesive bothers you, then try Skin-Prep wipe on pads underneath everything. But remember: You need to dry it with a hair dryer, it WON’T WORK if it’s even slightly wet. (Air drying isn’t dry enough, no matter how long you wait.)

From my experience…Rickst is the man to be listened to for our Dex issues!

Thanks Rickst for the detailed response. Sorry if I was repeating a question…I read a lot of posts, including the info on your page (very helpful) previously but couldn’t remember anything about scar tissue. Sometimes the response from a search is never-ending! I used Skin Prep and then Skin Tac before the insertion. And the next day I put flexifix just around the transmitter on to sticky pad. Do you cover the entire thing? I found the 4" width at
I think I might be a lucky one with adhesives…they don’t seem to bother me. Thanks again for all the info!

Skin-Prep is purely a barrier, keeping sweat away from Dexcom adhesive AND Dexcom adhesive away from skin. Skin Tac is more of an add-on adhesive, making Dexcom’s pad stick better- like Mastisol.

I don’t use Flexifix around or over the Transmitter unless I’m about the pound the IPX-7 rated “water resistant” clips and seam with high-pressure water from a spa jet. Instead, as you’ve figured out, I cover the entire Dexcom pad- because it’s all about the edges of the Dexcom pad pulling away from your skin. By sticking down a large piece of Flexifix, extending 1/4" to 1/2" beyond all of the the Dexcom pad edges, you keep the Dexcom pad locked in place. Right now, we’re exactly opposite from each other: I actually cut a doughnut hole in my Flexifix for the Transmitter clip area, because that allows the remaining FlexiFix film to lie totally flat against the Dexcom pad.

My Skin-Prep coverage, of course, extends to the entire area covered by Flexifix. But, if you’re not bothered by adhesives, you won’t need to do that. The Flexifix edge is less prone to damage from daily life because it’s extremelythin, and the plastic film stretches/shrinks to stay in contact with your skin when you move around. Dexcom’s pad stretches only a tiny bit-- and once it’s been stretched, it never shrinks back to fit properly. It’s left “too big”, creating air gaps underneath.

Thanks for the Kudos, Lisa! But, you’ve given me a great opportunity to remind everyone: I’m not a medical professional, licensed or trained to offer qualified advice about ANYTHING related to Diabetes care! Everything I say is just the personal opinions and experiences of a totally non-expert patient – so be careful, and check with qualified people before trying any of my ideas. They’re off-label, and entirely at your own risk.

Hi Courtney,

I am going to take an opposing view to most of the comments posted thus far. To understand my stance you can view another post I made on TuDiabetes (link below) and a post I recently made on another forum (which I copied below).

For the reasons in the 2 posts and as a compromise, I will only extend the Dex 14 days and try not to get marathon usage out of each sensor even though the sensor is still giving me accurate performance. I am not as confident as others that science can or has managed to fool the human immune response. I have to note that I have 100% coverage for the Dex, but can appreciate that those who do not will have to make other economic decisions

As with all things diabetes, YMMV. Evaluate the data and make the best decision for your diabetes.


  2. Post From Another Forum

    I agree with tedm, that the CGM sensor does not cause as much scarring as an infusion set, but I believe that scarring is still occurring.

    First, we don’t have long term data (10 - 20 years use) for CGMs. No one to my knowledge has used them that long.

    Second, the introducer needle used to place the sensor is of a larger diameter than the sensor and will cause a mild injury that will need your immune response (IR) to repair.

    Third, any object that your body recognizes as foreign is subject to attack from your IR. The presence of insulin is not necessary. To test this, place an extra infusion set on your body, but do not infuse insulin through it. See how long you can keep it on without the site becoming sensitive or inflamed.

    Fourth, as someone with T1 diabetes (caused by an autoimmune response) and alopecia (another IR), I can say that the IR can be activated at the cellular level against even tissue with your own DNA fingerprint.

    The researchers in this article also agree that the IR is at work, albeit at a slower pace than with infusion sets.

Many good points here! But your note about IR caused by physical damage from the large inserter needle (which I strongly agree with), leads pretty directly to my idea that “fewer of these violent insertions/removals is inherently better than more numerous insertions” … but of course, this only lasts only until IR from other factors becomes a greater consideration, or the Sensor wears out.

I think that your suggested test (i.e., an infusion set without injection of insulin) is a very poor “stand-in” for Dexcom’s Sensor wire: Stainless Steel is much more stiff and likely to create a larger amount of motion and tissue tearing over time; Most “soft” infusion sets are more highly textured; and the Chemistry is slightly different in all of these cases . I tossed a search for “histological response to teflon” at pubmed, and saw several papers documenting attempts to create new materials with better properties.

Your main point, if I may dare to choose one for you ;; is spot-on: The body will ultimately try to encapsulate anything which it recognizes to be foreign. It’s quite possible that a smaller number of BIG encapsulating growths is “worse” than a larger number of smaller growths. Thanks for the reminder, you da man! :))

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          BTW, firm massage with scar-reduction gels (or even the smelly old standby, Udder Cream) has always done a good job of reducing surface and SC scars for me. (I use Udder Cream, because it seems to work nearly as well and it’s MUCH cheaper.) Just don’t use them while the sore is brand new, and still “open”. Wait a few days for it to “calm down” before massaging the remaining scar tissue. As always, YMMV.

I routinely wear mine for at least two sessions (so 14+ days) and I don’t have any scar tissue from the sensors after a year of almost exclusively using the sensors on my arms (I use my thighs sometimes too). The only reason I’ve sought out other sites, is when my skin has become too irritated from the tape I use over the sensor to keep it on. The actual sensor site is invisible within a day of removing a sensor… I don’t personally think it’s doing any kind of hidden damage.

For the record, it’s not the dexcom tape itself that bothers me, but the combo of adhesive + flexifix that is pretty hard on my skin when it comes time to remove a sensor… wearing it is just fine, but I’ve actually had my skin scab over where I’ve pulled the tape/adhesive combo off, even when I’ve use a remover. However, I’d need this same tape combo to keep the sensors on for just one session, so I feel it’s a small price to pay to successfully wear the system.

Sarah, How do you feel about it on your thighs? I have found that I really am not comfortable with my infusion set on my thighs (normally on the outer part of thigh). How do you avoid putting pressure on it while you sleep? I’m going to try my arm after i get more comfortable with the insertion and I’ll need to do it by myself-a bit trickier!

Courtney,I have read that some women have no problems sleeping on the sensor because they are slender and the pressure is not so great. I cannot wear a sensor on my thighs or lovehandles because I weigh 208 pounds. I tried and my numbers went crazy. With my next sensor I used the center of my lower ab, and there was no problem at all.

My thighs are my favorite place to put the Dex (5’10", 158ish). My last box of sensors didn’t want to cooperate though. Not a single sensor lasted longer than 10 days. All of them did great for the first week, but just crapped out between 8 and 10 days. The last sensor looked pretty mangled when I removed it. The tip of the sensor wire just kind of fell off 30 seconds after I pulled it out. I was a bit shocked.

Where do you put it on your thigh?

Hi Rick,

The blank infusion set test was not meant as a comparison to the Dex sensor. The reason for the infusion set sans infusion was a reply to those who contend that it is purely the presence or absence of insulin that determines whether or not the IR is activated. If this were true, one would be able to place a blank infusion set on their body indefinitely, without IR activation. Substances in insulin may hasten the activation of the IR, but the IR will activate nonetheless.

PS: Thanks for the tip on scar reduction and Udder Cream