I just started with the Dexcom 7+ 3 days ago. Once I got over the initial ‘drifting’, which my doc said was normal variance of my meter and Dexcom readings in the first 24 hours after starting a new sensor, I have really loved it so far. Still trying to get used to not sleeping on it (it is inserted in the lower side of my abdomen as recommended by my doc, and I am sleeping on that side due to being pregnant), keeping it within range, etc…
My question is in regards to calibration. In the literature that comes with the Dexcom it stated that in general the more times you calibrate, the more accurate the readings will be. My doc said that you must be careful as to not give it too much information, and to calibrate when I have a stable (sideways) arrow showing under the readying. I know you have to calibrate a minimum of once every 12 hours. What is a good rule of thumb for calibration?
I have also found that at times when my Dexcom is surprisingly accurate (Dex reading of 106, One Touch Ultra reading of 104) the Dexcom will reset itself further away from what my actual meter reading is–say at 92. What gives?
Any comments or tips relating to calibration techniques are greatly appreciated!
I calibrate first thing in the morning when I wake. Then through out the day I keep tabs on it. If by lunch time or after the 3 hours of me checking after a meal it seems off, I calibrate it again just to get it in sync (I dont always do this). I also calibrate when it tells me to before bed. But if not, I will do the 2nd official calibration before I go to sleep. Other than that, I dont calibrate mine more than 3 times. Most of the time its good for the 2 calibrations.
The Dexcom rep that helped me start over the phone said that the more you calibrate, the more inaccurate it becomes. She told me to calibrate at the 12hr marks (a little before doesn’t hurt) and then to calibrate only if your meter is off by more than 50pts. So far, so good. I’ve only had an issue once and it was a sensor that DexCom replaced. It kept telling me that I was over 400 when I was getting 120-150 on my machine.
It helps that she is also a diabetic and has been using it for years! She also warned me to keep the transmitter piece out of kitty’s reach because she has lost a couple that way!
Thanks for the feedback. I also have another question…What if it is time to calibrate but the Dexcom is showing a rising or declining (either slowly or rapidly) arrow. Has anyone found that it is better to calibrate only when it is stable or is anytime ok? I am nervous to wait for the prompt to calibrate in case my level isnt doing the optimum thing (staying stable) when it tells me to enter a reading.
My Dexcom Clinical Manager told me a slight variation to the calibration story. Every 12 hours for calibration and EVERY TIME you dose insulin you should do a finger stick. If an insulin dose and calibration are within 30 minutes, just do the dosing stick. The other point was - except for the initial two entries, there should be at least 10 minutes between entries into the Dexcom receiver/calculator.
Hayley,
I only calibrate when my BG is stable. I don’t hesitate to push out the calibration to the next morning when my BG is not stable at night. Here is my reasoning: If at the time of the calibration my BG is very close to the Dex readout then the calibration should have no effect. I might as well skip the calibration. Skipping the calibration or delaying the calibration seems to be a more sensible choice than calibrating the Dex when the software has to guess the delay between BG and ISF. The software does not do a good job at this guesswork. For about half of the calibrations my BG is within 5 points of the Dex readout. This is evidence that most calibrations can be skipped without harm.
Hayley,
First of all, i was told that i can calibrate every time i check my sugar. My doctor said that it is okay to do it every time i check. Even if my sugar is saying 67 and double arrows going down, and my sugar is 80, i punch in that sugar to the dexcom unit. oh! dexcom says that the range for the for what the unit says and the meter is allowed to be 30 points off. I dont really like the idea, but it is what it is. I hope i was helpful:)
Your doctor’s advice seems to be more tailored to Minimed’s calibration guidelines rather than Dexcom’s. My Dexcom trainer/rep said you can calibrate at any time and that you won’t confuse the sensor by over calibrating it. I was told to calibrate at a wide range of levels, ie low, high, and in range and the sensor will become more accurate at a wider range of bg’s.
That being said I don’t calibrate with straight up and down arrows (rapidly changing) and I don’t calibrate when I’m low as I’m treating and I generally only calibrate two or three times a day. I will do an extra calibration if I happen to be steady but higher than usual or a bg in the 60’s or 70’s if it’s not dropping rapidly. That has worked really well for me. My Dex consistently reads very close to my meter readings at all levels of bg. Because of Dex I’m spending more time in range though.
Because the Dex is 10 to 15 minutes behind in reading your number from BG (Dex does not get the info from Blood), therefore it is not a good idea to calibrate when the arrow is not stable.
I calibrate Morning and night before eating. At lunch, only if I want to have carbs and want to bolus, I will check my BG before any bolus, and I feed it into Dexcom.
Just recently have avoided any carbs for lunch. Find it much easier.
I do have off days, but most of the time my Dex is very accurate. This Sunday, when the readings were very off, I realized it was because of a very long hot shower I had just taken (it is freezing in New York), so I took the transmitter out, dried all the moisture with a hair dryer and put it back.
I’d go cautiously in calibrating when it is off by >50 points. I’ve found that when I calibrate at those times that I often get the dreaded ??? screen and that sometimes means no data available for an hour or two! I wonder if it might not be better to use finger sticks during these times when the dex is having a hard time following glucose trends and then calibrate when things are at a more even keel? You may be able to shorten the period with no or bad data that way. Anyone else have suggestions on this?
Hayley, I missed your question in the 3rd paragraph. There is a very complex formula in the reciever. It runs a statistical probability about “how sweet” you are based on the electricity being generated from the sensor compared to known values (your finger sticks) and then massages the numbers to project a displayed value. That being said - it is a tool. I have had my Dex 7+ for about 1.5 years (on second transmitter) and I get a finger stick dead on about once every 3-4 months.
Cheers for the pregnancy!
