Ok, I know this has been talked about and talked about and talked some more, but I’m going to open it up again.
Situation is type 1 47 years, pumping about 27 years, Dexcom for about 4 years also used Medtronic’ CGM awhile back. Three basal profiles off, work and weekend work(crazy & earlier start time).Each profile has 2 or 3 rates. Carbs range from 1:10 to 1:13. Correction ratio is 1:110. Average about 20-25 units per day. I don’t low carb as I love my burger and fries and Mexican food!
I hear so many people who dose off their Dexcom and now it has been approved for dosing. My problem is there are times it’s right on and than times when it’s 60 points off. 60 points is a huge number and if I dose off it wow, I could be in a world of hurt.
So here’s what I currently am doing. I only go 7 days as I am in a trial and get my supplies free and they could really pile up if not using correctly and when in a trial, you really need to follow the guidelines. I usually use arm but sometimes upper stomach. Follow all procedures inserting and have only had one failure over the years. When receiver says to calibrate after warm up, I do one test and wait 15 minutes to do second test. I also only calibrate when asked and only when in that 80-200 range. Even when it’s way off, I let it ride. Most times it catches up but wow it takes a long time. My clarity report says I calibrate 1.8-2.0 times a day so i don’t over calibrate but I guess I should when off by 60 points. One of my major frustrations is that in a matter of 15 minutes, the arrow can be straight down, than angled 45 degrees, than up 45 degrees, than straight up. I feel like I just never know which way it’s going to go. And I just don’t have the time to just sit and stare at it.
And sometimes waiting for that “bend” to happen can take forever. Two days ago, pre bolused at a blood sugar of 100 and 60 minutes later still no bend. But had to eat due to heading into work. It worked because I didn’t have that post meal spike but where is he bend?
So long winded, sorry and hope I have all the details anyone in e know might need. But am I doing something wrong or am I just one of those that will never be able to dose off their CGM. And heaven help me if because it has been approved for dosing, what will happen to my number of test strips allowed?
With a correction ratio of 1:110, using your Dexcom reading to dose an insulin correction is riskier for you than those of us who are less sensitive to insulin. (My correction ratio or insulin sensitivity factor ranges from 1:28 to 1:37.) Now if your correction dose is small, like 0.1 units, then your risk is much smaller, too. But if your Dexcom reading suggests a correction of one or two full units and your actual blood glucose is not as high, like actual 180 (10) versus Dex 252 (14), that could mean trouble for you. In that case I would hesitate to dose on the Dex alone.
I will do calibrations if my Dexcom reading is greater than 20% off of my fingerstick number. This has been recommended to me by the Dexcom technical help line. I’ve even had to do a series of three of these calibrations, 15 minutes apart, to get the Dexcom back on track.
After watching and “waiting for the bend” before eating following a pre-bolus, I have mostly settled on using a set pre-bolus time for my meals. I picked these times using the “waiting for the bend” tactic to learn. I use 60 minutes for breakfast and 30 minutes for dinner. I will reduce this timing if my blood glucose is running below 85 (4.7) or so.
While I know that some payers have a policy of strip limits, most of them will entertain an appeal for a greater number if the doctor will submit the necessary paperwork. There’s also the ultimate backup of paying out-of-pocket for cheaper strips.
Terry, thanks for getting back to me. And I guess I will be of those that can’t and probably shouldn’t dose from my Dexcom. But I just want to make sure I am not doing something wrong here.
So when I start up a new one, do first calibration and wait 15 minutes to do the second one
Calibrate only when it asks for it and only when in the magic 80-200 range.
And if meter and sensor are way off, I should recalibrate. But my question to this one, is one calibration enough because I find even when I recalibrate it doesn’t pull into line. Over a few hours it comes into line but not right away.
Thanks again, and just want to make sure I am on the right page and getting the most from my equipment. You’re the best and thanks!
I’m always surprised by the many posts I see on here re: inaccurate CGMs—my Dexcom is usually very accurate (often even within the first day, typically for up to 3 weeks) and my A1c always matches my 90-day estimate perfectly. My only exception has been one very off sensor that I removed only to see that it clearly hit a blood vessel going in. That said, I only use my lower abdomen for my sites, so I agree that perhaps while alternative sites can technically work, if they are not producing good results, better to stick to the abdomen. Maybe arms etc just don’t work for everyone?
I read that other people also space out their initial calibrations by 15 minutes. I’m not sure of the source of this advice and I don’t think it’s harmful but it will make you wait another 15 minutes before getting the first BG number displayed on your receiver. Here’s the instruction from the G5 users’ guide.
I interpret this to mean two consecutive fingerstick BG readings one immediately after the other. I’m not sure if you’re using the G5 or G4 so I’ll look at the G4 users’ guide, too. Here’s the pertinent info from the G4 manual.
Take 2 separate blood glucose measurements with your meter, and enter the blood glucose values into the receiver (see Chapter 7, Section 7.2, How to Calibrate).
Like @Tim35 says, these words do not say to wait 15 minutes or not wait 15 minutes.
Dexcom customer service sometimes recommends additional procedures that are not documented so perhaps this 15-minute spacing of the first two calibrations is something they recommend in certain situations.
Both of these manuals caution not to calibrate when blood sugar is rapidly changing. They define rapidly changing as single straight up/down or double up/down arrows. As an added precaution, I try to limit calibration to times when the arrow is horizontal.
The manuals also say to limit calibrations to fingersticks within 40-400 mg/dL.
I agree that back-to-back calibrations make the most sense. Something I read somewhere said the Dexcom is like a new clock. In the beginning, the clock doesn’t know what time it is; you have to set it. So when you initially calibrate your Dexcom, you’re telling it, via two very close together tests, what your BG is – what time it is – right now. If you tell your Dexcom what your BG is with one test and then what it is with another test 15 minutes later, it doesn’t have an accurate, single starting point upon which to base all its subsequent readings.
I think I got the space the start up during calibration from Rose here. She seemed to be the go to person on this topic and have been doing it for a few months now & haven’t noticed any difference in accuracy. I have come to realize that I will just be one of those we can’t dose from my CGM. And that’s ok, was just wondering if I was making things worse.
Hi Tim,
Thanks for the feedback and while I said I use my arm, I don’t just use my arm. The one I have in now is in my abdomen and it reads like the ones in my arm. So I think, it’s just me. And as to correction factor, it was 1:100 up to about two months ago and just bumped it to 1:110 due to huge drops. I am in that stem cell study here in San Diego, so you might think I had background insulin production even after all these years, but one thing they checked for was no insulin production, so that is not it. And we have worked very hard at getting basal rates in line, down from 19 total to 11 per day. I again, have come to realize, there is no normal when it comes to diabetes and for many things, I don’t. Which is why I hate when doctors throw us all into the same treatment plan. What works for one, won’t work for the next.
That all being said, I love my Dexcom & wouldn’t trade it in, even if I can’t dose from it. My hope will be that my 8-10 test strips won’t go away if insurance companies think we only need the two to calibrate.
I don’t get the whole “wait 15 minutes” thing in part because it doesn’t make sense mathematically as a way to improve the system’s ability to factor out meter error. Entering two readings seems designed to minimize the amount of error that the initial calibration is based off of, given that your meter inevitably has error in the readings it produces. If your two back-to-back readings tend to differ (I use a One Touch, and mine definitely do), then having them right in a row would provide the most accurate information since what the algorithm is doing is using two points to estimate your true blood sugar (although, really, three would be ideal but I’m guessing it adds not enough extra reliability to be worth asking for it). When you add time into the mix, now it’s estimating two things—both the change and the error—it has to decide whether the difference between the readings is due to error or real change. It seems like you’re far better off with a model that only has to guess about one (the error), which is a simpler equation, leaving less to estimate and potentially get wrong.
