Now that I’ve used this thing for a few months (Medtronic 502 w/ CGMS Sensor) I have a few observations, not all of them positive, and would like to find if others are getting the same results.
First, I had to fight Blue Cross for the system, they declined repeatedly. When I made the final appeals out of their system, the state of California overruled their declination. I’m happy it worked out, but it became essential when I no longer could feel the lows.
Unfortunately the system is not really accurate, but provides only approximations under the best of circumstances. It is a tremendous improvement over the 15-20 times I was testing daily. My fingers have permanent pin holes everywhere. I know, we all do.
Most of the solvable accuracy problems in my experience seem to be caused by 2 factors:
- The sensor readings lag behind the meter readings by as much as 3/4 hour. This is acceptable, but means the warnings for your lows come to late. The solution, for me, is to set the warning higher (around 80) and keep track on an ongoing basis of whether you are going up or down.
2.The warning beeping alone isn’t enough because the CGMS is simply not accurate.
Accuracy is a big problem all the time. But if your initial calibration is off, you can’t fix it buy adding input. Start over.
Your initial input can be off because you screw up and put in the wrong number, but more often you are trying to calibrate when your sugar is low, high, or in the process or rapid change. Any of these conditions will really screw up the first calibration. Unfortunately adding more meter data does not seem to help. I don’t know for sure, but it appears adding more data just causes the meter to average what has been input. Each addition brings it closer, but if you start way off, it does not fix the problem.
You can fix it most effectively by getting your sugar under control, then telling the meter you have a new sensor. As others have noted, you don’t have to wait 2 hours when you trick your meter into stating over. When you start over the calibration begins with a clean slate.
If you begin the calibration with blood sugars between 100 and 180, the meter operates with results amazingly close to those of your meter, but are still time delayed. Often this gap is as low as 10-12 minutes.
If you calibrate when your blood sugar is below 80, or above 250, the system will read wildly inaccurately until you clear and start over. Also, if you calibrate, for example, when your sugar is at 80, and then immediately eat and take insulin, you greatly confuse the sensor. Sometimes it figures it out, but often you make a mess. It really does work best to start over, and stop trying to fix it. Often the 3 days is gone while you fight with the meter. Then you find bliss when you start the new sensor period. Don’t endure the agony. It does not seem to save on sensor life. And you are not a failure because you give up and start over. You own the darn meter, it doesn’t own you. REALLY.
Keep in mind that the meter testing is required every 12 hours (I know, we all thought the finger sticks were a thing of the past), and extreme sugar levels, low or high, will also screw up your future accuracy. Fortunately update high or lows do not seem to throw the sensor off by as great an amount. If you input a 350 though (because you forgot a bolus or ate pizza and guessed wrong, either skip the 12 hour data (understanding this will cause trouble) or just start over as a new sensor when things get straightened out. Once you input a 350 or higher, you can forget the readings ever returning to anything close to accurate.
So this is my input. It may be wildly inaccurate for you, but it’s what I’ve encountered in trying to figure out how to make this thing work.
So do I like it? Absolutely. Even though it can be wildly inaccurate , when calibrated properly, it works reasonably well. While I can’t rely on it to accurately warn me of lows until its often to late, if the calibration is set right and the alarm goes off at 80, I know to check. If I see it is trending down and I get the 80 alarm, I check with the meter. Often I’m at 50 or 60, and still coherent enough to do something about it before I become the belligerent ■■■■■■■ who refuses help. And if the warning is wrong (or is right and it is just below 80), that’s great. I don’t mind finding I don’t have a problem if the darn thing keeps me from embarrassing and dangerous lows. And my friends and kids greatly appreciate not having to deal with me “in trouble” as often.
- I love the Nexcare waterproof abrasion cover sold at Walmart. They are relatively inexpensive and much more flexible, removable and durable than the things Minimed sells (IV3000 by smith and nephew). It takes a little practice not to destroy them taking them out of the package, but it actually works just like the directions say if you take the time to read them. If not, you’ll figure it out after you wad up the first two taking them out of the package. You can guess how I did it.
By the way, I don’t like the ones Nexcare sells with the bandage pad in the middle. You may prefer them if you don’t like having to peel the sucker off your sensor, but I find the ones without the bandage area stick better and last longer.
- I don’t know how the other posters here get 21 days out of sensors. I’m lucky to get 6-7 days before I get the “Lost Sensor” message, and no amount of new sensor starts or “Find Lost Sensor” attempts work anymore. Is there a secret I haven’t found yet? Please tell me.
- I hate the sensor warning beep. It is a generic electronic sound used for everything from warning of cell phone batteries dying to trucks backing up. It is in the sound range where anyone with mild hearing problems can’t hear it. You will discover people telling you you are beeping everywhere. And I find I don’t always feel the vibration since I’m a belt wearer. Has any one figured out a way to change the tone the way you can with cell phones. I’d love a distinctive tone. Something like a screamed “Your blood sugar is low and you are going to pass out” would be just fine. So if there is a techie out there who can advise, it would be greatly appreciated.
Thats it. I have no expertise. I’m an estate planning lawyer, for heaven sakes. And I’d love to hear whether others have similar experiences of suggestions.