Replies to This Discussion

Permalink Reply by MF44SRQ on January 17, 2013 at 5:45am

I had a similar experience the 1st week, then it settled down. I'm 3 months into it and it's rarely off more that 5% with my OneTouch. Hang in there...

Permalink Reply by QQMary on January 17, 2013 at 6:03am

Thanks..Hope the machine will get adjusted soon. I got the G4 so I can get more sleep and worry less, ironically i get less sleep and had to check more often because of these false alarms :(

Permalink Reply by MikeU on January 17, 2013 at 6:11am

Don't forget that the Dexcom sensor is not reading blood glucose directly. It uses the interstitial fluid to calculate/estimate blood glucose. When you check your BG with your meter 8-10 times, make sure you are entering that BG into your Dexcom to help calibrate it.

I started a new 7+ sensor last night. At 2:30 AM, it read high then ???. My meter read 174. So, I took a small correction bolus. Then, at 6:45, the 7+ read low (51, I think), while my meter read 104. At 8:00 AM, my meter & 7+ were close.

As far as I can remember, I can't think of a time when my 7+ read normal when my meter read very low. Maybe it happens, but I wouldn't be surprised if the Dexcom was programmed to err on the side of protecting against that - leading to more false low alarms.

I've been using the 7+ for about a year and a half. Every sensor & sensor location doesn't behave the same. Sometimes, it's just off, but overall, it's more than worth the price of admission.

Permalink Reply by A. Kelsey Metcalf on January 17, 2013 at 6:26am

My first sensor on my G4 was AWFUL! I called dexcom and they said to put in a new sensor. I did and its been smooth sailing ever since. I would insert a new one and if you have the same issues, call dexcom.

Permalink Reply by Clare on January 17, 2013 at 6:32am

I always call the first few days with new sensor the "marinating" time. The sensor is getting used to you and you are getting used to the sensor. My first night with the G4 in November my husband and I got literally no sleep. It was beeping I was high it was beeping I was low it was horrible. Since I had not had any training and was just "winging" it I emailed my CDE about it. She said initially set the low alert as low as it will go which in this case is 60 and don't even set the high alert. After that first night things went a lot more smoothly. I didn't get too many warnings and slept a whole lot better. Now several months in I understand it much better. If I go low I treat the low as I normally would and although the Dex will still be reading "low" or 51 or something like that I just wait the 15 minutes and retest. Invariably the sensor is still reading low and my blood sugar has returned to normal or near normal so I calibrate and it usually "believes" me and the reading doesn't go as high as I have entered, it goes to at least above the "low" limit. The interstitial fluid that surrounds the sensor is about 15 minutes behind the blood sugar so it usually takes at least another 15 minutes for the sensor to begin reading closer to actual. I still have not got any high alerts set.
I have noticed that where I wear the sensor also effects how accurate it is. Although on Dexcom support I always say I am wearing it horizontally across my abdomen in actual fact I have found the readings when it is placed vertically on my arm are a lot more accurate and I get the best readings on my thigh. But as in everything else in D yours may vary. I have also found that the sensor gets more accurate the longer it is worn. So while the Dexcom folks and FDA require you to change the sensor every 7 days I find the second week of a sensor is better than the first and although I have not personally gone beyond 14 days, some people get good results into a 3rd week.
I wish you all the best with the G4 I truly wish it had been around when I was pregnant 22 years ago. It does take some patience but once you get in the groove it makes life with D a lot easier IMHO.

Permalink Reply by QQMary on January 17, 2013 at 7:06am

Thanks all for your response, very helpful. A quick question though - Would it be an issue if I calibrate too often?? The minimum suggested is twice a day but does it help if I calibrate every 3-4 hours?

I'm still planning to check often during the entire pregnancy, should I enter my BG into the sensor everytime it's off?

Just worry that it might screw the algorithm if I calibrate too often. Thanks!

Permalink Reply by MF44SRQ on January 17, 2013 at 7:09am

Stick to twice a day. Too many calibrations will make the meter less accurate. For the first couple of weeks I was still finger sticking 8 times a day, but once the device settled in, I only test 2 times a day for calibration.

Permalink Reply by MikeU on January 17, 2013 at 7:16am

I can't imagine that you could calibrate "too" often. I would think the meter reading directly from the blood would always be more accurate than the sensor calculation from not blood.

Not sure how you were taught, but I was taught to take the two startup meter readings from different hands. I had never done that before and was more than a little surprised when my meter gave me very different (in my mind) readings from each hand. I can't recall the exact numbers, but I was very surprised by difference. So, now I don't think anything of a 10% difference between two different meter readings taken at the same time.

Permalink Reply by MF44SRQ on January 17, 2013 at 7:19am

Read this post about calibration
http://www.tudiabetes.org/group/dexcomusers/forum/topics/g4-calibra...

Permalink Reply by MikeU on January 17, 2013 at 7:31am

I'd be curious what Dexcom has to say about whether it's good or bad to calibrate frequently. The finger sticks are definitely bad, as is carrying around the meter and paying for supplies. But, those are different issues than the accuracy of the Dexcom.

I don't think the Dexcom "can" be as accurate when your BG is changing rapidly. Mine certainly isn't. The Dexcom is not reading from your blood. There is a built-in delay before the interstitial fluid reflects BG changes. The Dexcom needs to calculate this to get the reading it shows. The G4 might do this better than the 7+, but I can't imagine how the G4 could have eliminated this delay and (estimated) calculation.

If being pregnant causes rapid changes in BG, I'd think the Dexcom is not going to be as accurate. Personally, I'd think it is better to have it than not have it - but I'm certainly not an expert. I'm sure there is some additional information available by searching for "dexcom pregnant" or similar terms.

Fwiw, I was taught that it would be better to always use my meter before injecting insulin - whether it's a correction or at mealtime - not absolutely necessary, but better.

Permalink Reply by MF44SRQ on January 17, 2013 at 7:36am

My Dexcom rep said to not calibrate more than 2 times a day, 3 at the most. I carry my meter regardless because if the sensor fails (happened twice so far), you have to have the meter available. For the 1st month, I did a finger stick before taking a bolus, now I only calibrate for breakfast and dinner so I can stick to 2 finger sticks a day.

Permalink Reply by MikeU on January 17, 2013 at 8:00am

Interesting. I don't think I was told to calibrate a certain number of times - just that the Dex would ask twice.

My Dex is not as accurate when my BG is changing quickly, especially at lows/highs and with a new sensor. I just find it very difficult to believe that entering a meter reading at those times could possibly make the Dex calculation less accurate.

Of course, an important issue (mentioned in the calibration thread you suggested) is the accuracy of the meter reading. One post in that thread seemed to suggest not entering too many meter readings, in case of inaccuracies. Personally, I'd think that's all the more reason to enter more meter readings. One inaccurate meter reading when entering 2 per day is a pretty high percentage of inaccurate calibrations.

I agree about taking the meter. It's part of my daily routine. But, if I'm only going out for a few hours, whether going on a bike ride or to a hockey game, I'm pretty comfortable leaving it at home.

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