Tuesday, 19 March 2013

Dexcom G4 Sensors - Life Tally

It is the diabetes community's worst kept secret that Dexcom CGM (Continuous Glucose Monitor) sensors last well beyond the seven days they are approved for.

While I am not a diabetes professional and would never recommend using a sensor for longer than the approved seven day period, I do bend these rules myself. I may not be a diabetes professional, but I am a professional diabetic; I manage this beast full-time and have had to find ways to make CGM a more full-time part of my self-care.

In the UK, there is no such thing as medical insurance and as yet there is no guidance on providing diabetic patients on the NHS with sensor funding. This will change one day, I hope. But until it does I have decided to fund my sensors myself and at £62.50 for each sensor, wearing them for only seven days is just not an option for me; being more economical with them is the only way I am going to make this work.

In fact, it was one of the reasons I chose a Dexcom in the first place.

So I have made the decision to wear each sensor until:

a) the sensor expires naturally
b) the results become unreliable/inaccurate
c) any irritation occurs (indicating my body may need me to remove the sensor before an infection occurs

I have decided to keep this tally of my Dexcom sensor lifespans out of interest; mainly my own, but I suspect there may be other people out there with an equal interest.

I hope you find it useful.

______________________________________________________________________

Less than 7 days
7-14 days
15-21 days
22-28 days
29-35 days
36+ days
0
2*
14
11
1
0

           ______________________________________________________________________


* These two sensors laste 8 and 11 days respectively, on a holiday when a sauna was being used daily.  Having never had another sensor last less than 14 days I believe these conditions contributed to 'early fail'.


Post-script:  I have changed the chart to just hold numerical information for ease of reference.  

45 comments:

  1. Hi. Can you explain what you mean by 'expired naturally', and especially 'expired naturally but remained accurate until the very end' - did you consider sticking with that sensor until it became unreliable?

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    1. Hi Lesley,

      Expired naturally really referred to it ending on its own without either a) becoming irritated and me removing it if it has been in some time, even if it was still still giving good numbers (once it irritates it should probably come out) or b)not me knocking it out or some other external factor.

      By 'expired naturally but remained accurate until the end', I mean it was on day 13, still giving great numbers but eventually I got what I call 'the question marks of doom' symbol for several hours, where the sensor could no longer read glucose levels. So rather than a slow petering out where numbers are no longer that reliable, it kept going very accurately until the sensor just 'gave out' and could no longer read.

      Does that help?

      You've actually reminded me to update this page as I started keeping a Tally on the Facebook site to try and draw more attention there. This is probably the better site.

      How are you finding the first few days? Don't be overwhelmed by numbers at the moment. That initial phase does stop and you start to normalise to having all the numbers there.

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    2. Yes thanks, that does help. I thought the question marks of doom were just 'your 7 days are up' but I guess it's the final 'your sensor is no longer useful to man nor beast'.

      My first not-quite 24 hours have been a roller-coaster in many senses! Daunting when I first took the kit out of the packet, wonderful when I managed to put the sensor in, great to get so much instant help on Facebook, exciting to see how closely it matches my fingerstick tests right from day 1, and a BG roller-coaster because I'm hanging on in with sub-cu until Tuesday when I get my long-awaited new DiaPort!

      I downloaded an article by Gary Scheiner about interpreting CGM data in the first few days. http://integrateddiabetes.com/Articles/cgm/cgm%20data%20analysis%20for%20dsm.pdf

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    3. Ooh good luck with the Diaport - I bet Tuesday is a looooong awaited day!

      The sensor ending warning is very clear and obvious. It comes up with a specific screen to to say 'replace sensor soon' and a timer showing when it will run out (very useful to know when it will run out so you can time the new 2 hour windown well - it's a pain having to do a calibration BG at 2am!).

      The question marks of doom appear from the book (from memory) to be a warning that something can't be calculated. It has happened once or twice during a perfectly good sensor session for no reason, but it usually short lived and comes back on again. I had it once when I was lying on it - so think it can mean ANY kind of interference.

      But when it was on there after 13 days of a sensor and for several hours, I took the jump that the sensor had expired. So DON'T pull the sensor as soon as you get this; it could be a temporary interruption of some kind and it could well find itself again and carry on giving great readings. Mine has done that several times, usually at night.

      I've only pulled it when I've been fairly sure the sensor is naffed and I've never actually had the 'failed sensor' symbol yet.

      It's great that you've had such a good experience so far. For me, it is definitely preferable to the Enlites. The calibration at any time, the incredible accuracy (and therefore trust), the extended time (currently on day 16 and it is still within 1 mmol all the time) and the comfortable wear beat the Enlites hands down.

      Will check out the article, thank you :)

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    4. Thanks again Anna - that makes it all much clearer!

      Now I just need to ensure the surgeon doesn't rip off my precious sensor on Tuesday!

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  2. I am somewhat at risk for diabetes, and am considering getting a CGM to have more awareness of how my blood sugar level behaves.

    I was wondering about your experience with the sensors. Once the sensor is in, is there any remaining irritation with having it in your skin? Can you safely take a shower without destroying the sensor?

    Good to see that the CGM doesn't automatically shut off the reading after the 1 week "limit" (I'm assuming?) Just wondering if you've noticed accuracy dropping off as you go past the "official" lifetime?

    Thanks!

    Note - since getting a CGM while not diagnosed with diabetes may seem extreme, I'll add that I'm an avid follower of the #QuantifiedSelf movement, and am looking for / using a wearable ECG, pulse oximeter, GPS, etc =)

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    1. Hi Sam,

      Thanks for stopping by. I'll try and answer so everything makes sense!:)

      The sensors are waterproof provided the transmitter (the bit with Dexcom G4 written on it) is safely snapped into the cradle. This protects any water from entering for up to about 30 minutes I believe.

      The sensor itself is completely painless, you won't feel a thing. Some people do get irritated by the tape though so you could be one of the unlucky ones. I've personally never found that.

      The sensor turns itself off after 7 days, but I simply leave it where it is and select 'new sensor' as though you have put a new one in; this fools the system into thinking you have a brand new sensor in. I'm now on day 12 of the sensor and still going strong :)

      The longer you use a sensor, the more accurate it gets as you calibrate it at least twice a day. So, the first day you have only calibrated in once or twice, so it is still being programmed to what your blood glucose is doing. People tend to find the longer you have it the better it is. Eventually as the sensor begins to wear out it will become less accurate, but I tend to find that happens at the very end of sensor life, which can vary depending on the sensor as you can see from above.

      With regards to not actually having D, there may be a couple of issues getting one. Firstly, it is a super expensive bit of kit, so if you were getting it for interest's sake and to have a try here and there, it may be worth looking around at the cost.

      I am not sure how it works in the US (sorry, not too sure which side of 'the pond' you're on) but I believe you have to be supported by a clinician to get access to one. In the UK you can buy the system from a distributor called Advanced Therapeutics, but we get a discount as it is a product for a medial condition. Although it is still the same product, I don't think you can claim as you don't technically have the condition. For Animas to sell them, you also have to show that you are being supported by your diabetes clinic in the use of them, so you'd have to get from Advanced Therapeutics (who are more expensive).

      I hope some of that has been useful for you, and if you have any other questions just let me know

      AP

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  3. Hi Anna,
    I seem to run short quite quickly and badly at evening mealtime. So I was thinking of using the Dexcom to alert me before this happened. But as you know, the cost is horrendous.

    From the User Manual, the sensors appear to have Start Sensor and Stop Sensor commands. So to extend the sensor life, I was wondering if I could:-
    o Start the sensor at (say) 4:00pm, and then Stop it at (say) 7:00pm,
    instead of leaving it on all day. Do you know if this would work or not?

    Also, is possible to remove the sensor when it's not in use - and re-insert it later. The User Manual implies that the sensor says inserted until it expires. But it doesn't explicitly say you can't remove it and then re-insert it. Do you know if this is possible or not?

    Many thanks

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    1. Hi Peter,

      I'm so sorry for the delay - don't you hate it when work gets in the way of life?! :)

      The first point about turning it on and off - I am honestly not sure of how this would affect the sensor life, but as they are designed to give you continuous readings, I don't imagine it would prolong the life as the sensor is continuing to sit in and interact with the fluid around it; it just wouldn't be feeding results to your handheld receiver.

      The other thing is the sensor is calibrated with a blood measurement, which is done a minimum of twice a day. The sensors are usually accurate straight away, but are known for becoming all the more accurate the longer they've been in (remember that the idea is to give you trend information, rather than specific numbers. As it happens my G4 is usually very spot on, but it is still out by may 0.5 - 1 mmol fairly regularly). If you were turning it on an off, you wouldn't be calibrating it as often and would therefore not always have the most consistent use and calibration. Think about an algorithm - the more information you put in, the more accurate the result at the end. It is the same with CGM.


      The sensor definitely cannot be removed as it is inserted with a needle, which is then removed, leaving a hair like sensor. This sensor is flexible and moves a little under the skin. If it were removed, it would be too bendy to get back in again. I expect there would be health ad safety issues even if it were possible as once removed from the body and stored it would no longer be sterile. But either way, I'm afraid they aren't removable.

      Do you use an insulin pump? The best way to explain it is to liken it to the teflon cannulas which are inserted using a needle and the needle is then removed.

      I hope that answers some of your queries, even if it isn't the answer you'd hoped.

      It is worth mentioning I have discovered that Animas sell the sensors for about £70 less per 4 sensors than the other main distributor in the UK, and I am currently wearing a 27 day sensor. So my sensor use this month has cost around £47.

      Best wishes

      Anna

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  4. Hi im jack and I just wanted to know if you have any tips for the dexcom G4 I just got it and im kinda learning it still so if you have any tips please tell me

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    1. Hey Jack, I'm so sorry this took so long! I recently posted this blog (http://insulinindependent.blogspot.co.uk/2013/06/costly-business.html) about how to make some of the costs cheaper. Hope that helps.

      The other thing is I now use Kinesio tape to keep it stuck down longer and keep the sensor tape lasting longer.

      How are you finding it?

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  5. Hi Anna, I've been thinking about getting the G4. Can I ask how do you keep the sensor attached...... after showers, sweat and 2 to 3 weeks of life I would think it's adhesive would be useless?

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    1. Hi Noel,

      To start with when I put it on I use something called Skin Tac, which is a sterile adhesive used for dressings/cannulas etc. It goes mega sticky and hardens after a few minutes, giving an extra stick. That keeps it going for about a week even with gym 3-4 times and lots of activity.

      I also use Kinesio tape over the plaster after a few days, and change that every few days to keep it good and tidy. Then it will last as long as I keep looking after it. Kinesiotape is the tape that athlete's use so it is flexible, breathable, durable and a really decent quality, That helps hugely.

      Hope that helps! :)

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    2. I also use the G4 - I too use Skin Tac wipe before applying, but cover the whole thing with an IV3000 (or Tegagerm) patch from the word go. This seems to

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    3. Anna:

      Now you have been using the sensor for several months, how long on average do you find they last? Any change over your original post?

      I have been using Medtronic CGMS sensors (self funded) for the past 3 years. My pump is now well over 5 years old and due for renewal. If I could get 20 days out of a G4 sensor (compared to around 10 for the Medtronic sensors) it would make sense to switch to an Animas Vibe pump and the Dexcom sensors.

      Delete
    4. Hi Joel,

      I get between 14 and 20 days. I switched to using my abdomen where they don't last as long, but with it being summer it was much nicer to have bare arms.

      With arms my average would be around 18 days.

      I know one guy who only ever gets 12 days, but *most* people I speak to get 18-25.

      Hope that helps

      A

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  6. Wow! we use the G4 for my son but have never gotten more than 7 days from it. No idea how we could extend the life of the sensor; it just says replace sensor soon then shortly dies. Wish we could get a few more days...Jeanne

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    1. Hey,

      When it says replace sensor, rather than putting the same one, you can do 'start new sensor' using the one that is still in. It will re-start again. I did it today! :)

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  7. Interesting to read experience of others - I've been using the Dexcom G4 since November - also a UK self-funder. Anna, thanks for the tip about buying from Animas... has saved a lot.

    That said, my current sensor seems to be amazing and is just going on and on... is now on day 50 ! Arm site + cleaning skin with alcohol swab before insertion + skintac wipe (but leaving a tiny non-wiped bit of skin where sensor goes in) + IV3000 patch over the top (replaced every couple of weeks as needed) seems to do the trick. Coupled by massaging the site - often first thing in morning - if get ??? (or even the clock symbol or 'sensor failed' errors).

    Think you must be lucky to get BGs within 1mmol of the fingerstick. I've never had quite this accuracy (on arm or tummy) - more like 2mmol.

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    1. Hi, I am just verry curious, how were your blood sugar levels during the 50 days. It seems to me that the sensor life corelates with blood sugar levels. The better blood sugar it is the longer it lasts the sensor. My first sensor was perfect accurate and lasted 33 days with perfect blood sugar, the second sensor lasted only 14days with quite bad bs levels, 200mg dl. Thanks.

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  8. I got one of these a week ago and I loooove it, its the closes ive ever been to not being a diabetic. I am on day 8 and am finding its still attached well, Im very active both at work and in spare time and will likely order skin tac once summer comes around to keep them on longer. I use 3m Clear medical tape to manage adhesive edges lifting, and find that after showers and baths a hair dryer works well to make sure the adhesives are still sticking ( obviously with caution as to not overheat the sensor )

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  9. Excellent web site & British too! Thank you Anna.
    I'm on my second G4 sensor, on my stomach. I stopped the first after 3 weeks, concerned about possible infection-it was still functioning. Apart from some adhesive marks it was difficult to tell where the sensor had been.
    My second one is now on day 41. I had one "---" & Dex asked to me recalibrate. I thought that was the end but it has been fine ever since.
    I was going to change it tomorrow (6 weeks), but the 50 day message above & my wallet are making me think again...
    I used Skintac before inserting, then used it to re stick the edges of the Dexcom plaster after about a week. Since then I've applied 4 pieces of Hypatape also stuck down with Skintac.

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    1. Hi DunePlodder (love the name!). And yay for the Brits! :)

      I have actually been terrible at updating this! I've now been using for over a year and LOVE the length I get. Although I have never managed as much as 40 days! My current sensor is 15 and going strong! :)

      It sounds like we have very similar sticking habits - I'm sure skintac spares many a lost sensor!

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  10. Hello,

    What is the Animas web site in UK , how can i reach them ?

    Thanks

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    1. Hi,

      You can reach them on http://animascorp.co.uk/

      Just to warn you, they now only supply sensors to Animas Vibe customers. At the time this was posted they still sold them to everyone, but had to change that.

      Good luck! :)

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  11. I know I'm more than a year after the original post with this comment, but thanks for explaining in the comments section how to get extra days out of your dexcom. I started using it when the dexcom 7+ was the newest version and upgraded to the G4 when they stopped making the 7+ sensors last year. I had always heard people say they got extra time out of their sensor, but didn't know how because mine always shut off automatically. I can't believe I never thought to just "start a new sensor" on the receiver without changing the sensor in my skin.

    Also, having read through the comments, I thought I could answer a question asked awhile ago from someone in the states wanting to use the dexcom for "pre-diabetes". In the states you need a prescription from your doctor, not only to have a portion covered by insurance, but even just to order it from dexcom. And, according to a conversation with my endocrinology clinic when I first got the dexcom 7+, the sensors fail much sooner than the 7 days period if there are no fluctuations in blood glucose (as you would expect from a non-diabetic) - apparently due to not calibrating properly, although I didn't really understand the full explanation and didn't question it since it does not apply to me. All of the doctors at my clinic wore a demo/trial system for a week to get the experience of wearing and using it. I think they reported it failing after 3-4 days when a non-diabetic person is wearing the sensor (again, this is with the old dexcom 7+ version).

    Pam

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    1. Hi Pam,

      I'm so sorry I missed this! Apparently the blog no longer notifies me when comments are posted!

      So glad you got the extra days out of it. I would never have realised either if I hadn't heard people taking about it. Now I more than double how long they last!

      And thanks for expaining the second point, too. Crazy how much it varies from country to country

      Best wishes

      AP

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  12. Just found your site after Googling "restarting dexcom sensor". I have a brand new G4 and was doing my first restart after the first 7 days. Thanks for the post earlier in the comments - made it easy. Great chart, too! I'm going to be putting mine in Excel. Best, john

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    1. Thanks for commenting John, how are you getting on with the chart/sensors?

      Best wishes

      AP

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  13. Hi, I am looking at self-funding the Dexcom in the UK. I have autonomic dysfunction (dysautonomia) and several other conditions with stupidly long names. Anyway my blood sugar fluctuates way too much I am Hypo a good times a day that I can identify and get on my BM machine. My BM will go high also but due to my Hypo's. Im not classed as diabetic, my HBA1c tends to be in the 4% range because of so many hypo's. These are obviously affecting me at work and driving and are all down to my body not been able to control its own hormone production. Do you recon a CGM is a good way to go? I have been advised it is an option but would have to self fund and it seems better than finger pricking excessive amounts. Thanks Charlotte

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    1. Hi Charlotte,

      Sorry for the delay - as I mentioned above my blog no longer notifies me when someone comments so I completely missed this!

      It sounds like CGM would be a good idea for you. Have you explored it any further?

      AP

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  14. Have you noticed that the lifespan of the sensor would be related to the insertion site?I have had longer lufespans in the arm, up to 25 days,, in the belly area about 14-16 days.

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    1. So sory Ella I've only just seen this - not sure comments are being sent to my email anymore! The sensos which lasted the longest were my upper arms. But I did notice later that if I lie on one of those arms more at night, I get site irritation much more. So I often weigh up if it is starting to feel sore and decide to take it off.

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    2. Hello Anna:
      Loved all the comments. My wife uses dexcom G4 and have been thinking of extending the use of the sensor beyond the recommended 7 days. She has it on her abdomen and would like to try it for 10 days to start with. Also which is the best place on the arm to put the sensor in your experience?
      Thanks
      Suryanarayana

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  15. i am going abroad soon and have heard that you cannot put the dexcom g4 or sensors through the xray machine or metal detector - help!

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    1. Not true. My wife uses dexcom G4. We traveled abroad Nov.-Dec.2014 and my wife went through all the X-ray machines without any problem. I was more concerned whether the security people would ask her to remove that but that did not happen.

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    2. This comment has been removed by the author.

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    3. Do you mean she put the receiver in her hand luggage which was then x-rayed and she walked through the metal detector? what about spare sensor, can they also go through the x-ray machine or in the luggage in the hold which gets very very cold?

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    4. Yes, she had it in her hand bag. The sensors might have been either in the carry or our luggage.

      Delete
  16. I'm a new G4 user. How do you get the transmitter back in the sensor after taking it out after the seventh day?

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    1. don't remove it!!!! simply hit start new sensor after the dexcom tells you it has expired. If you remove it, it is tough to put back.

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  17. you don't take it out after 7 days, just 'stop sensor' on the receiver and then immediately re start it, you will then have to wait 2 hours will it reconnects to the sensor. if you have taken the transmitter out just clip it back on pushing the narrower end in first and then press the wider end in, you might hear it click in twice

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  18. Hi,
    I have the Dexcom G4 for the last 2 months and love it. But lately, when I change to put a new sensor, I have been getting the '???' right after putting in a new sensor. It doesn't calibrate and when I take the sensor out it has blood on it. Can the blood cause the sensor to fail? Most of the time it has been working very well but to have 3 sensors fail in 1 shipment is a little weird and I was wondering if I am doing anything wrong. BTW, I am inserting in the belly area and will try arm next!
    -
    DD

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  19. I have been using Dexcom for over 2 years. A few times I got as many as 10 days out of a sensor. My biggest complaint is that about 25% of my sensors fail before 7 whole days and am getting tired of calling them to have a free replacement sent. I am disappointed with this aspect but I do love the Continuous monitoring with trend graph. At least I have not had any Lows requiring medical EMT response.

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  20. I have been using the Dexcom CGM for several years and am currently on a G4 combined with an Animas Vibe pump/receiver. I am wondering if anyone has issues with getting the temporary (<3 hours) ??? error after bathing or swimming.

    We discussed this at my pumpers group meeting earlier this week. Someone stated that if moisture gets through the water resistant barrier between the sensor and the transmitter, this error results. It can be rectified if you remove the transmitter (leaving the sensor in place) and wipe (or blow with compressed air) the contacts on both the sensor and transmitter dry. If done quickly, you can reattach the transmitter without having to restart the session. He also mentioned this error can occur if you put pressure on the site for an extended period - like sleeping on it. In the latter condition, massaging the site to get the interstitial fluids flowing will usually fix it.

    This water issues seems to happen to me more frequently the longer I leave the sensor in place. I exercise daily and shower at least twice a day. Does anyone have experience trying to cover the sensor/transmitter with a suction cup or other device while bathing/swimming? If so what do they use?

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