Anybody else getting CGMS readings that wildly disagree with meter BG's?

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Permalink Reply by AndyRozman on November 19, 2008 at 10:10am

Hi Angi !

Difference comes from point where your measure BG. If you measure from finger you get real value, but since CGMS reads from different place, you get different value... Theoretically after 15-30 minutes, value on CGMS should be the same as measurement from finger. As for difference between finger and CGMS in points... This difference will never be the same.. For example if you BG is falling very rapidly, difference can be bigger... And since CGMS is experimental device, this things can happen.

Andy

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Permalink Reply by Alicia on November 19, 2008 at 12:07pm

Yesterday, it was amazing! The CGM and my bloodsugars were exact, that only happens once in a while for me. Usually they are pretty close BUT some days I wonder why I am wearing it because they are so far off. I guess it really depends on when you calibrate. But Andy was right saying that these things can happen because it isn't 100% yet.......

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Permalink Reply by Rickst29 on November 20, 2008 at 9:57am

Hi Angie. For me (Dexcom), the first day is MUCH less reliable than than the following weeks. It seems as if the "warm up period" really needs much longer than two hours to stabilize.

I never got good results from MM when I tried it (about two years ago). But you might be having the same effect which I have on Dexcom. Usually, when I'm having really bad results after the warm-up, it's a lot better to just restart the thing than it is to enter additional calibrations. new calibrations make adjustments to the "flakey" numbers, the flakey results are still being used. A full restart (with a fresh two-hour warmup) clears things up instantly.

And, have you tried some alternate sites? my frontal abs never worked as well as my love handles or butt cheeks. I know that for appearance and clothing issues butt cheeks might not be viable, but love handles (near the belt line, straight below the ribs) might work better for you too. If you sleep on your side, though, you'll need to make sure that your Sensor is on the "up side", and not being squashed against the bed.

Slightly OT: After you get used to CGMS, and get somewhat more reliable results, you can correct FAR more aggressively than you used to. This is because you can look at the graph 2 hours later and see the trend (slope of the curve)-- if it's falling too fast, you just pile on some quick carbs to prevent the hypo from ever happening. Sometimes I add carbs at bG levels as high as 130-140, because I see that I'm gonna fall through the floor in the next half hour without them. Dexcom has been found to be faster at showing lows during drop off periods by several people who have used both, but it is fast enough-- you'll just need to learn watching the trend, rather than just the bG value (as you've always done with finger sticks.)

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Permalink Reply by Liz on November 20, 2008 at 8:29pm

I've found that my Minimed sensors are not the best at tracking high BGs and that's when I see the biggest difference. During the night it's even worse (for catching highs) and I've woken up close to 300 while the sensor said 180, but the same sensor would track fine during the day.

I believe other people have mentioned that their sensors just don't catch highs very wekll. I have my High alert set to 160 because if I set it any higher, I'm afraid my BG will be out of control by the time the alarm sounds.

Also, I think the trainer was supposed to tell you to expect differences up to 20 percent, not 20 points. Everything I've read and have been told said 20%. So, unfortunately, the 194 vs. your meter BG of 241 falls into that +/- 20% range (barely). I find that most of mine, other than when I go high during the night, are much closer.

Oh, I also think the sensors don't catch lows too well at night either! I have my low alarm set to 75.

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Permalink Reply by Rickst29 on November 20, 2008 at 9:34pm

Liz, you might be pushing the Sensors for too long: When they're dying from insuficient reagents left, MM Sensors do pretty well on normal bG but refuse to cross a line, say 150 mg/dL, to match a high. No matter how much higher your bG really goes, it barely budges above that erronious "maximum".

Lots of us think MM is slower than Abbott, or even Dex, at alarming the lows it DOES catch, and more likely to miss lows without alarming at all. My Dex seems almost right on bG without delay when I'm going down, but it's late/delayed when I'm going up. MM seems to have about the same delay in both directions, I've no idea why.

If you end up sleeping on the Sensors, maybe try an alternate site? "Stale" ISF leads to totally whacked numbers, and I think that compression on the site tends to prevent the ISF from getting "refreshed" via blood flow.

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Permalink Reply by Liz on November 21, 2008 at 8:33pm

Even a brand new sensor with a good Isig will lag at night if my BG rises. I believe Minimed has told people that inactivity can lead to the sensor flatlining, or not tracking well. I pretty much like to sleep at night, so yeah, I'm pretty inactive then!

I know a sensor is dead when the Isig drops to a low single digit and stays there even when I push my BG a little higher. I change it then. I'm amazed when I heard that some people can get 3-4 weeks from a single sensor.

The sensor I had in up until yesterday was working great. Right after eating dinner and for the next two hours, it kept telling me I was low and the Isig was in the 4 range, so I knew it was dead and removed it. That one was on day 9.

I usually insert the sensors on my lower abdomen but in September I tried my arms for the first time. My left arm was so-so but every sensor I've inserted in my right arm was a winner right from the start. I wish I had a few extra right arms to use! I try not to use it for 2 weeks after removing a sensor. I've tried my upper abdomen but it wasn't tracking well, and my one leg site so far didn't work out.

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Permalink Reply by Alicia on November 21, 2008 at 9:45am

my alarms are set higher and lower for the same reason......to catch them early. My low alarm is set at 90 (I have no low symptoms) and my high alarm at 200 (it used to be 180)

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Permalink Reply by Jaclyn on November 21, 2008 at 12:54pm

My experiences have been very similar to this. Almost every time my CGMS says 70-75, I'm really in the 50s. Maybe it's just not quick enough. A lot of the time it'll be spot on again after I come out of my low!

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Permalink Reply by Alicia on November 21, 2008 at 9:41am

I had an experience yesterday (thursday)....just after my wonderful day, I changed my sensor and the new one gave me problems from the beginning. I think I hit a blood vessel or something. After 5 Cal Errors during the day I finally decided to remove the sensor after it told me I was 70, 200, 350....all within 10 minutes! When I removed it, it was a gusher..... the blood had definitely traveled up the little tubey thingy and thats why all the readings were so off. Today seems to be a better day......keep your fingers crossed.

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Permalink Reply by Rickst29 on November 21, 2008 at 11:53am

yep, that sort of thing happens from time to time. I've asked for two "freebies" from Dexcom during my two years of usage, and they're happy to comply, even though the CS woman asked me to please plug it in the computer and send in the data over the Internet once.

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Permalink Reply by AUDREY on November 23, 2008 at 6:10am

Hi,

I also have a alot of discrepancies with my sensor but my doctor mentioned if your sugar is really high or really low the sensor could be way off when your sugar is in a good range the sensor is more accurate, So basically when you need it the most when you are high or low it does not work as well hmmmmmm. I also heard not to put adhesive patch over the whole sensor to cut in in half it keeps in flatter I have not tried it yet but my friend does it that way she uses her sensors on her leg I tried that but whenever I would change or have to use the bathroom I would hit it or pull it out no matter how carefull I was.
I tend to use my stomach for the pump and sensor it is sensitive there though and that stinkin needle to put the sensor in is way tooooooo fricken big excuse my language it hurts like hell and it think and way to long I hope they change that soon. I have had a bad batch of sensors too I am not a fan of mini meds customer service. I have to say when I had a animas pump they were always very nice and helpfull I am looking forward to them working with dexcor for the sensor next year I think I will switch to them.

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Permalink Reply by Mollie on November 25, 2008 at 6:46am

Sometimes it takes 48 hours for me to get good on track readings. Sometimes i get good readings from the start. When i get a sensor that is consistantly off...i do my best to try to get it in line...sometimes it just does not work. It could be placement - i have found that certain sensor locations work better than others - but that was thru trial and error.

good luck...once you get the kinks worked out, you will love it.

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