Short Lasting Sensors

I keep wanting to respond to the group messages but what is happening with my Dex seems quite different than what I see others are saying. I want much more understanding before I try to help other Dex users.

My first sensor lasted 9 days. My present sensor lasted only 5 days and would not renew itself like the first one did. Is that unusual? My biggest frustration is that my Dex wakes me up several times each night with low or high number alarms. At no time have those numbers been correct. When I am approaching the bounds of my range (70-140) the Dex goes crazy and goes well beyond the boundaries and sounds the alarms. All this means that I am testing several times during the night and losing sleep. i think I will not wear the Dex while sleeping anymore. I may just wear Dex while awake since that is when my BG’s vary most due to eating and exercising.

Hi, Richard.

My experience has been that it takes the Dexcom 24 hours to begin generating accurate results. During that first day, though, it tends to exaggerate every fluctuation it sees; for instance, my bg may drop from 100 to 75, but the Dexcom interprets that 25mg/dl drop as having been a 50mg/dl drop, and the <55 alarm goes off. So, I wind up keying in correction readings frequently throughout that first day.

Keeping this in mind, I never place a new sensor in the evening, because the first few hours produce the most frequent alarms. Ideally, I place the sensor on a weekend morning, so it’s only interrupting me around the house (instead of at work). I also take it for granted that I’ll have to test quite a bit more than normal during the first day of a new sensor, but once the sensor is dialed in and generating reliable results, I can test less frequently, often skipping my pre-lunch and pre-dinner fingersticks. I typically test 8-10 times a day; during a sensor’s first day, I bet I test 15-20.

Since upgrading to the 7+, I find that I can usually get 10 days from each sensor. Maybe one out of every 10 will fail within five or six days, but most last for at least seven days.

(Standard disclaimer - I am not a doctor, I am not your doctor, and I am totally unqualified to give medical advice. I can only share my own experience.)

Richard, I can’t say I’ve had the crazy alarms you have but I have had a couple sensors fail (or just be really off) before the 7 day mark. I’ve called those in to get suggestions on how to fix them and Dex has replaced them. If you’ve got sensors that aren’t lasting their full 7 days make sure Dex knows so they can look into it. I do find that Dex does usually alarm before my sugars are actually at the high / low marks (mine are set for 80 and 140) but usually it alarms at about 78 on the low side and 136 on the high side which is plenty accurate enough for me. Good luck figuring it out, I wouldn’t want to live without my Dex!

I have been using the Dex 7+ for a couple of months. My sensors seem to last from seven to nine days. I also have seen variations at night and as you can see from a discussion I started earlier today, after exposure to cold. I set the alarm at a top range of 220 and may reduce it to 200, but if I set it to 140 it would just be a nuisance. When it goes off in the middle of the night it has usually been within 20% or so the meter reading. A few nights I saw an unlikely pattern when as you described, it seemed to go crazy.

Thanks so much Andrew, Rebecca and Allen! I beieve I will change my range to 60-180 at night and back to 70-140 while I am awake.

I have to say that my experience is very much like Andrew’s. I don’t test as much as he does, but my sense is that the precision improves after 10-15 tests (about a day and a half of testing after changing the sensor)

I’ve been constantly able to squeeze two weeks out of pretty much every sensor in the last few months, with a few ??? at the bottom of the second week maybe, and some wild swings. I only had one failed sensor, lasted maybe 4 days and then started to give error on the receiver.

I too, like Andrew, insert a new sensor during the morning, so that by lunchtime the 2 hours calibration window is over, and I can eat without having calibration being confused by swinging BG.

On the quality of the readings, I find that the bottom of the first week and the first few days of the second week are the most accurate. Of course a proper calibration is very important, it is imperative to avoid periods of swinging BG to insert or restart a sensor.

Ciao, Luca

How does the bg graph look during the night? Steady and smooth or a lot of ups and downs?

I’ve been getting between 7 and 14 days out of all of them except one or two. I never get ??? for some reason. The first day of a new sensor is always a mess.

Mine stays steady and smooth between 85 and 105 almost every night. If I eat later than 8 PM that can give me a not so smooth curve until 4 AM. My carb and insulin sensitivity changes a lot as the late evening approaches. 1 unit will lower me 12 points during the day, 20 late evening and 30 while sleeping until 5 AM. One carb raises my BG 4 points during the day but 8-10 points while sleeping. Knowing these things helps very much with my control.

I was asking because the sensor does not like mechanical pressure. Your site seems to be fine.

Here’s a rule: Never, ever, wear the Sensor under your body (against the bed), or in a place which ends more than an inch or two below you heart. (Higher is good, lower is bad.)

Now, did you break that rule (which I probably never told you before), or is it something else? I can make other guesses, but let’s start with that one-- poor circulation causing ISF to go “stale” around the wire, or actual pressure squeezing ISF away from the wire completely.

Rick, thanks for your response. You make it seem like you wear sensors on your rib cage if they are never more than two inches below your heart. (Is that really what you meant?) I have permanent scar tissue on my upper abdomen and cannot place infusion sets there. The guide clearly states the sensors are ideally placed on the abdomen. My first Dexcom sensor did not work well on my upper abomen either. I am using my lower abdomen and it is much better.

I have been sleeping with the sensor somewhat against the mattress and under my side. I guess this means my love handles are inappropriate locations for sensors. Thanks!

I don’t think I’ve ever followed either of these rules and my Dex seems to work fine. I generally wear my sensors on the sides of my stomach. This leaves me sometimes sleeping on them if I sleep on my side. I need to have the receiver close if I do this or I’ll lose the signal but the numbers have never been off. The vertical placement of mine is usually about a half inch to two inches above my belly button. I find that if it’s lower it gets caught in my pants’ waistband and higher gets uncomfortable 'cause it’s in my ribs. Rick, I’m glad you’ve found something that works well for you, I just wanted to offer another perspective and experience.

As you know from private message, I use love handle sites. Remember that your heart is INSIDE your body, not at the surface of your skin. When using love handles, you want to sleep on your side (the other side, keeping Sensor up high.) Obviously, when sleeping on your left side, your right love-handle is way higher up. Less obvious, maybe, is that your heart is only slightly to the right of your mid-line-- even if your chest is much bigger than your waist measurement, your love handle will be above your heart.

Summary (after way too much detail): Your site selection is great, you just need to FLIP OVER when you switch Sensor sides. Sensor side up!

etta, you should try pre-starting when you’re in a position to predict (or to decide) when the end is near: Shoot a new Sensor into it’s new location, but don’t tell the Receiver anything about it (and don’t remove the Transmitter from the old one).

That way, you get 10-24 hours of “extra” warmup" before the two-hour countdown even starts, and the first day problem won’t occur. I can personally get 14-17 days from each Sensor, but I always put in the replacements on the night of day 12 before going to bed, and switch over during the following day. (Late in the morning, after the time for all of my dawn-effect craziness has passed.) The old ones never die at an inconvenient time, and the new ones are a lot more reliable (with the extra 10-11 hours of warmup piled on top of the the standard two hours.)

Great post, Rita!

One thing I never mentioned anywhere is that the mattress-squash “issue” seems to occur much more frequently with men, because we’re heavier. (It’s just like the Sleep-Number bed commercials, in which the DW gets by with a setting of “35”, while the DH needs “85”. Those are very typical figures for couples using such beds.)

So I’m not at all surprised that you don’t experience a problem. Thanks for the report!

I tend to wear mine just under the sternum, center stomach. I’m on the 13th sensor and have had 2 failures. All the rest lasted at least two weeks and gave accurate resuts after about 6 hours. The best accuracy was the second week.

Hi Rita! Thanks for your advice. I have been moving my Dex sites around just like I do for pumping. I do lie on the transmitter when I am on my left side. If that affects the numbers then it would not be a problem after I turn over or get up the next morning, do you agree? This morning Dex said I was 40 and the arrow was pointing due south. I tested at 102. That is a major gap. I was lying on my right side at that time with no pressure on the transmitter. I fed th 102 to Dex and it reset at 79. It has been working well since I have been out of bed.

My problem with Dex is that it is close to my meter numbers only when I am 80-120 but is useless when I am not in that interval. I realize some of you are pleased with Dex because you can rely on trends, and I understand that. My trends are faultu though. When it says I amd rising/dropping fast/very fast I am NOT doing either, most of the time. So both the numbers and the trends are faulty and useless. i am doing finger sticks 20 times per day checking out the useless information.

I also had much trouble when starting my pumping in 2007. My endo gave me wrong numbers and i had BG’s 300+. I had to delete all her numbers and program from scratch. It took 3 months before I was happy with pumping. I am a patient individual. I will give Dex a total of 3 months before deciding to quit, or not.

It takes at least 1/2 hour of activity to “freshen up” the ISF around a squashed Sensor. During that time, you should NOT enter the conflicting bG readings as calibration points, because the Sensor doesn’t yet have “valid” voltages from “good” ISF. You’re distorting the curve… just use those bG readings to guide your first hour of activity, and calibrate Dexcom later.

Turning back over to the proper side during sleep time is a much slower recovery, because the tissue surrounding Dexcom is totally inactive; your breathing RATE isn’t all that much slower than active waking time, but the STRENGTH of the muscle actions is much less. YMMV, of course; for you, the entire night might be unrecoverable after the initial squashing mistake.

I know that your outstanding A1C implies very little time spent above bG 140 mg/dL, but to widen the “reliable” range, you should be sure to enter calibration figures when that does occur. (At the time it levels off in the Dexcom, not while it’s rising. For me, this occurs 15-20 minutes after the bG increase has ended.)

If the upward/downward trends are STILL wrong, after you’ve stopped feeding it “bad” calibration figures at times when you’ve got particular reasons to expect inaccuracy (e.g., bed-squashing), then this site doesn’t work for you: Try elsewhere.

Your insurance/financial situation might make a 3-month test relatively painless, from a financial perspective. But I would be watching the calendar like a hawk, to be absolutely sure that I notified Dexcom that it’s failed to work within the 30-day money-back trial period. Notify first, and tell them that you’ll try some other sites if and only if they fax you a statement guaranteeing your right to a full refund for an additional 30 days beyond the standard policy.

This is because many people have switched from Dex to Navigator, and gotten much better results. After you get your money back, or assign the refund back to your insurance, you can try the other one. (Abbott and MM don’t have such a refund policy; that’s why everyone should try Dexcom first.) If Dexcom doesn’t work for you, don’t apologize-- I know darn well that it’s certainly NOT your fault-- you’re obviously not (ahem) inexperienced in Diabetes Management, or clueless about Math and Science.

Is the Sensor Pad getting loose around the edges before it fails?