Minimed Constant Glucose Monitor

Happy New Year! As promised a follow up to my earlier post in which I detailed my changeover to an insulin pump with constant glucose monitoring. As described on December 12, I’ve been using the Minimed Paradigm 522 with the Guardian constant glucose sensor.

If you’re completely bored by this and follow my articles of travel, restaurants, clubs, and Denver life – you should skip this and read my story on American Airlines flight 1469. However as insurance starts to cover this equipment more type 1 diabetics will be utilizing this and similar monitors – so hopefully this will help those new to this.

In brief: Pager size insulin pumps are used by type 1 diabetics in lieu of injections. Pumps better mimic the pancreas by giving a constant dose of insulin with manual doses at meals or as needed. An ancillary gadget called a “constant glucose sensor” sends your current blood sugar reading to your pump, providing you with a constant stream of blood sugar numbers and direction of blood sugar level – rather than the lone number obtained from a finger prick.

Overall it’s an incredible life changing tool for a type 1 diabetic. Knowing the TREND of your glucose is something that was only in the realm of imagination for years. Now, to be aware and know your blood sugar minute by minute, WITHOUT the need for (as many) messy finger pricks is an enormous step forward. And to have to blood glucose number sent directly to a small screen is a wonder of med-techy synergy.

Here are the drawbacks. Well not exactly drawbacks, but things to be aware of in order to develop your own workarounds and methods to match your daily life.

Appearance: The sensor and transmitter piece aren’t quite as sexy looking as the photos. It’s necessary to cover them with a small dressing. No big deal – the starter kit includes transparent adhesives. Medtronic sells a pack of 100 at the astronomical price of $62, but you can find similar at Walgreens for under $5.
New Sensor Obligation: When starting a new sensor you need to allot yourself a seven hour block of “awareness time.” Better said: keep your meter handy.

After starting a new sensor you’re required to enter your first BG in two hours, then another in five hours. It’s not practical to start a new sensor late in the evening, as you’ll be alerted to enter a BG in the middle of the night. After the two and five hour BG calibrations you’ll be prompted for one BG entry (calibration) every 12 hours. This is pretty easy, and I’m getting used to “thinking 12 hours ahead.” For example if I do a calibration at 2pm, I have to remember to do one around 10pm or before bed so my pump doesn’t wake me up at 2AM requesting a calibration. Typically morning and early evening is best, (before meals,) as your BG needs to be relatively stable for the best calibrations. You can set your calibration reminders up to four hours before a necessary BG entry. But again think 12 hours ahead. If you’re planning to sleep in Saturday morning you don’t want your last Friday entry to be 6pm, or you’ll be harassed by your pump at 6am. This hasn’t been an issue so far as I’ve actually been taking MORE manual readings to test the accuracy.

Accuracy and Rapid Changes: During periods of rapid change the CGM definitely lags. If my BG is 200 and I lower it down to 100, my spot checks show it will be a bit slower to reach 100. BUT, I do show during normal periods of minor fluctuation it’s very accurate. Its stable periods (non-rapid change) it’s been leveling out matching my finger sticks within 20 points.

However I am bit disappointed in how it matches blood sugars that are rapidly rising. And I’ve found when my level is LOW and bring it up, the readings bottom out and take quite a while to reach up to where it should be. These “flat periods” and annoyances are similar to blogger Jay’s experience in this recent post. I see way too many of these stagnant periods when I KNOW my levels are changing, but the results are slow to follow and stagnate within 10 points.

Attempting to remedy this I’m experimenting with new sensor sites. I realized my last sensor was on a site where I’ve given myself many shots over the years. I’m on day two of a new sensor, placed on my upper leg, and am watching the results closely. Pasta dinner at Maggiano’s last night DID prove more accurate, although my manual checks showed little fluctuation anyway.

Sensor Life: When you start a new sensor the pump allows a three day use, and when expired instructs you to change sensors. Like infusion sites most users extend their sensor life to reach six to nine days. The “three day use” is only the number documented by clinical testing and approved by the FDA. There’s nothing unhealthy about using a site longer provided your body, (and awareness of accuracy,) are comfortable with it.

The pump sends you a “sensor end” message after three days. It’s easy to tell the pump you’ve “replaced” the sensor by selecting “Start new sensor.” Your pump will prompt you for a BG shortly, (usually 15 minutes, and not two hours from a newly inserted one.) And remember since the pump thinks you’re on a “new” sensor you’ll be prompted for the initial five hour check. Obviously there are accuracy concerns with using a sensor repeatedly, but as you learn how your body operates with the sensor you can make adjustments for that.

The sensor doesn’t like being soaked in hot water. Showers are fine, but hot tubs and baths reduce the life of the sensor. Thus if you’re removing a sensor Friday and planning on some hot tub soaking Saturday night, best to just start a new sensor Sunday as not to waste a sensor for just one or two day’s use.

Other Sensor Messages and Other Stuff

When flying you’re supposed to remove your transmitter from the sensor, and use the “Reconnect Old Sensor” feature after landing. (Or anytime after disconnecting the sensor from the transmitter.) Yeah right. I have no plans to do this. Flying is when I WANT my CG numbers as during travel my blood sugar fluctuates more due to eating crappy (or no) food. The range is less than 10 feet and not a threat to airplane safety. Minimed only tells you to do this because they have to. On a related note I took two flights over the past week and my pump and sensor did NOT set off security.

Lost Sensor: If your pump is out of range from the sensor for more than 40 minutes you’ll get a “Lost Sensor” message. Just hit “Find Lost Sensor” and you should get readings again within 15 minutes.

Cost: Unless you can stack your closet with an unlimited supply of sensors I recommend keeping your sensor life in mind when planning certain activities. As mentioned hot tubs, jello wrestling, or other activities in which you want to be “untethered from the sensor” require some planning ahead in changing of sensors. Unlike the pump you can do without the sensor and it’s readings for as long as you need to – it’s just normal life before the CGM.

Without insurance sensors are $350 for a box of 10. That’s $35 per sensor. A “wimpy” injection of your sensor can be a $35 mistake. And time consuming as well since you’ll be annoyed by “calibration errors” until you just replace it. If your insurance covers sensors with a nominal co-pay then of course you can be more liberal in use. However remember inserting a “new” sensor still requires the two hour window to start, then your five hour calibration. So even if I could afford a new sensor every three days I’d still use them longer to avoid the the calibration requirements.

Overall – grade B Balancing my expectations with my month of experience I’d give the Guardian a B, wavering between a B+ and a C+.  Each person needs to tailor their use and data according to their needs. Hopefully my experimentation with different sites will remedy my issues of “flat periods.” But keeping that in mind I still love using it. The technology WILL improve and get better, and realizing the potential it will be available to more and more people. I’ve found it addicting having the numbers at my side no matter what my activity.

If anyone is also using this or new I’d love to read your reviews. I find these almost as interesting and exciting as “How Air Traffic Control Works!” Take care and have a killer 2008!
James Van Dellen

16 thoughts on “Minimed Constant Glucose Monitor

  1. Just a quick follow up-follow- up from yours truly.

    My latest sensor has been much, much more accurate. My last two were placed in a fleshy area, where as this is on my thigh (side) and providing much more accurate readings.

    Last night I had dinner out, a few martinis, saw a movie, and after a 3.0 meal bolus and a couple .5 corrections during movie (thanks to the CGM up-trend) I manually checked it and it’s only three points off at 133 vs 136. Not bad.

    And these types of situations (dinner/movies/drinking) are exactly why I like the CMG: To make small corrections in food and bolusing when it’s inconvenient to take a manual finger stick.

    From what I’ve read the deeper the sensor is inserted the better. It avoids blood vessels which can cause bleeding, and obtains more accurate readings. And in my limited trials it’s been better to avoid fleshy areas, hence I’ll probably keeping using the more lean areas.

    This week the Guardian CGM gets bumped up to an A-

  2. James,

    Thanks for the great post and I will definitely have to do careful planning when scheduling my jello wrestling around my sensor start up. 🙂

    Thanks for the in depth tips. Do you mind if I link this post to other diabetic message boards I belong to?

  3. Just read your A- update, now I am soooo psyched for my 1/8 start-up. 🙂 Meal bolus errors, of which I do daily, are exactly why I need and want the CGM sooo much and ooo yes for my possible return of walking 18 holes of golf instead of riding the cart.

  4. Hi Karen – you’re welcome to use some quotes and link back to my post.

    I’ve gained a lot of info by reading other sites, and happy to share as well.

    Have a good weekend – and good luck with your transition also…

  5. Great article. You’re right, it’s very addicting. I’ve had mine for about a month and when I’m changing sensors I feel so at risk. Funny that I did fine for 18 yrs w/o it. I’ve had trouble with location too. I left my last one in 11 days because it was working so well I didn’t want to fight with a new one. I thought you were suppose to put these in a fleshy (fatty) area. Maybe I’ll try the thigh next time.

  6. An update for me. The first two weeks I had two good days and I gave it up and swore I would not try again. I was off it for two weeks and then was thinking about my long appeal process and the fact that it is covered 100% and well I tried again.

    Well I tried it again and I have been on it for 4 days and it has been running perfectly and very close to my meter, numbers wise. It has caught my highs for me to make corrections a bit earlier and my lows beeping me awake at night. I have also seen a bigtime rise in my bgs about 5:30 a.m. I thought it was my basal settings but today I slept through 5:30 and when I woke up I checked on my bgs and it did not rise at that time, so my basals are good. I am thinking it is either coffee, the stress of getting ready for work, as I am always late, or I need to increase my insulin to carb ratio for breakfast, but I think it is the stress of getting ready for work.

    If this thing keeps going this well, I am saying woohoo. I am hoping for it to continue for increase exercise during the warm months, without fear of lows.


  7. Hi Karen – thanks for the update. Good to read another newbie’s experience. Yeah it is weird to see what your blood sugar does at night. Medium spikes and dips for no apparent reason. My CGM does lag a bit behind my meter numbers – so I’ve learned not to overcorrect based on that.

    So even with the negatives that come with new technology it’s been useful for what I want – which is numbers when I’ve busy doing activities like skiing, out watching movies, eating out with friends – and other times I don’t want to interrupt everything for (sometimes) messy finger prick…

    All the best – james…

  8. Hi, I have a 715 Minimed Pump and am thinking of trying the new glucose sensor. My biggest question is “What about all the sticking on my stomach?” My stomach area is already kind of scarred from my infusion sites….does the sensor cause discomfort and/or scarring over time?

    What about “bulkyness?” Is the a too uncomfortably bulky to carry around?


  9. Hi Cale – Thanks for the interest in my story.

    I’m different than a lot of type 1 diabetics in that I’ve only done stomach injections a handful of times. I don’t have much if any fat there, so my infusion sites and CGM sites have been on my upper thighs and upper buttocks.

    The size and weight are not even a concern. Physically its about the same size as an infusion site, but as I noted in my post you do have to secure it with some tape (as the transmitter has no adhesive.) I make a large X which lasts until its time to replace the sensor of recharge the transmitter.

    I really don’t notice it at all after wearing it. Since there’s no “cord” like the infusion site its actually even LESS noticable.

    As far as scarring: I’ve only been using the insulin pump and CGM since November, and as mentioned been rotating it around my upper legs. I’ve had mine in as long as 14 days with no problem. I’ve also noticed that my infusion sites seem more effective in my legs than upper butt – perhaps because I’ve been giving myself shots there for 12 plus years.

    For concerns like scarring and adaptability I’d advise the standard disclaimer of checking with the doc.

    One really good discussion I’ve been following is at Misanthropic Scott’s blog – who is also fairly new to the Guardian. He details some “hacks” to get better accuracy and use, and I HIGHLY recommend reading his post and comments when you start out. It’ll defintely speed up the learning curve.

    Also Kerri at Sixuntilme has some photos of how the CGM appears on the body. Her experience wasn’t as positive as mine – but she has in depth reviews on the Guardian, also notes some info on the Dexcom – a popular alternative.

    Hope that helps. Overall I LOVE using a CGM. Once you start using the benefits and learn how to deal with the faults you’ll love it. It doesn’t rule our regular blood sugar checks – but being able to see your BG while at a movie, dinner, biking – or anywhere else you don’t want to stop and do a finger prick is invaluable.

  10. Hi I found your post while searching google.
    I was on the guardian now I have the CGM within my new Paradigm pump so no more wearing 2 things which is nice.

    But I have to say if your on the thin side like me trying to find a place to insert the sensor for CGM is so hard. I do not have a place on my body that does not bleed back pretty large amounts. Does anyone know if they plan to bring this one down to 6mm like they did with infusions sets?

    Anyway mine is always very accurate with the exceptions of rising and falling blood sugars the double arrow kind on the screen or in other words fast up and fast downs. However that does not bother me as much since I was told ahead of time of the delay. It has saved me a few times at night from some very bad lows and overall I have been able to reduce my insulin and not bounce around so much because of the data.

    When I get the double arrows in either direction I start watching close on my meter maybe even every half hour so I can really see what is happening. For me I can not tell you how much this extra data has meant. I am finally after 5 years of bouncing (10 years of type 1) starting to lessen them thanks to the CGM.

    I do have to take breaks though as I run out of places to insert but man do I feel a bit more safe. That is gold for me.

    Be well and Be loved

  11. But I have to say if your on the thin side like me trying to find a place to insert the sensor for CGM is so hard. Does anyone know if they plan to bring this one down to 6mm like they did with infusions sets?

    Thanks for the comment Laura. Since the sensor needs to access the interstitial fluid beneath a certain layer of skin I’m guessing there are limitations on how short the sensor cannula can be.

    I agree with you though that rotation can be an issue. I usually wear it on my thigh/upper leg, and never one my stomach. (I don’t do any injections there either.)

    I’ve taken breaks from wearing it too. I find the CGM most essential when travel or doing activities outside of my 9-5 routine. But weeks when I’m doing the routine my BGs are fairly predictable.

    Now that its been a year and the initial “cool” factor has worn off a bit and its just a regular part of my life I need to write a follow up.

    Glad its working out for you and thanks for the note. -james…

  12. I hope you keep writing the good and bad James I really like the knowledge base you and others seem to have.

    My Question would be if you are very thin wouldn’t you need less depth to reach the interstitial fluid?

    I can not go near my legs with a CGM. I have 2 places my lower hips that I go back and forth on and I try make the sensor last as long as it can. I don’t insert at the “correct level” but I make sure the sensor is in all the way. I use IV3000 tape since the others cause reactions and I tape the sensor down before I connect it to the transmitter.

    The helps if the transmitter gets bumped hold the sensor in I have to cut the tape though to make it work. Then then transmitter then a bubble tape wrap over it. So far I have been able to get 5 to 10 days out of a good inserted sensor. The paradigm gives me less “lost sensor ” errors then the Guardian did I have no idea why.

    Is your tummy beaten up from shots and such or not just a good place for you? Mine is beaten up so a few months break is needed. Everything sensor, infusion set even the short thin needles I use when injecting cause bruising and bleeding so off limits.

    Anyway I type talk to much you take care be well and always be loved

  13. Thanks Laura – I appreciate the good word!

    Actually I’ve never used my stomach for shots or sensors. Maybe one or two shots in eight years. I hit the gym regularly and bike a lot – so am fortunate to have a fat free abdomen (at least right in life.) Not that I’m a model or anything but I just don’t want marks (even temporary,) from shots. I don’t care for the marks the infusion sites leave either – again even if myself and my other half are the only people that see them. (That’s definitely a negative.)

    I do about 7-10 days with the sensor, and use some tape from Walgreens to make an “X” covering the transmitter and sensor. Works pretty well for me.

    As far as sensor skin depth I’m really not sure how it works. I forget about the annoying parts when I’m using the CGM and can quickly glance down for a BG reading. When I’m out with friends or at parties it for sure beats scurrying into the restroom or to my car. (Of course my close friends are used to seeing my constantly squeeze blood out of my fingers and my little test strips everywhere.)

    Remember as Brimley says: check yer blood sugar and check it offen.

  14. Thanks for the information. I have been a type 1 diabetic for 34 years (with no long term complications!). I’ve been on the pump for 14 years. I started with the Paradigm CGM about 1.5-2 years ago. I stopped using the sensor almost a year ago but have committed to try again. Hence, I am researching what people are saying worked for them and did not. I would like to make it work again—-although my doctor has commented that I probably should not think about it as an “all the time” thing but as a periodic way to get better information. I have trouble find enough sites to insert the sensor. I do get bleeding in my stomach (although not from lack of flesh). I had reasonably good results, I thought, when it was in my thigh but then I somehow knocked it out a lot. I’d prefer to put my infusion set in my thigh but was told not to because of the way my body would absorb the insulin when exercising. Do you put your insulin infusion set in your thigh?

    What kind of tape do you get at Walgreens?

    My next biggest frustration with the product is that I use all Mac/Apple products and I can not upload the data. You can not even upload via FireFox on the Mac. I assume you are not using a Mac, right? Last I checked, MiniMed just seemed to be refusing to deal with Mac users. Very frustrating. Luckily my husband has a Windows machine but given that he travels a lot, I hate to be dependent entirely upon his equipment to gather my data. I’ll have to read your more recent posts and see how you are liking the sensor still. Thanks!

    • Hi Amy – thanks very much for reading and visiting.

      I put rotate the infusion site from anywhere on the front/side of thigh (avoiding muscle,) around to the fleshy parts of the side towards the rear. I also agree the CGM is best used on an as needed basis, for reasons of convenience and cost.

      After two years of use, (this is an old post!) I don’t use it regularly when my life is an my auto-pilot routine – i.e. workweek and weekends at home. However when up skiing, traveling or occasions where blood sugars may be more unpredictable because of food or activity I find it an excellent tool – so I’ll start it before my planned activities and just leave it on for a few three day sessions and restarts.

      I do have a Mac at home, but I’ve never used any Mac or PC software with any blood sugar monitors or diabetes gear. The Paradigm Pump does have a 30 day history so you can easily see averages, and I get an A1C blood test every few months which gives me a three month blood sugar average. Plus I hate installing crummy software on my PC. That plus the extra work never made it worthwhile to look at those little programs, when I mostly care about my blood sugar day to day – (and keeping it as stable as I can!)

      I can’t recall the tape at Walgreens, but it’s with the other medical tape and about 1/2 inch width – which I used to form an X over the sensor. Has worked great so far.

      Thanks again for checking out my experiences — hope those answers help! James…

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