A couple of weeks ago I posted about how to make your Dexcom sensor last longer than seven days. This week I want to talk about some reasons for Dexcom inaccuracies.
The dexcom is an INCREDIBLE tool for diabetes management, but that tool is only incredible when it’s accurate. I get so sad when I see people giving up on their CGM too quickly because they got off to a bad start. Tho most of the time it works great (I’d say 95% of the time) there are times when it’s off.
Here are 12 reasons for Dexcom inaccuracies:
1. Bad Robot Parts
Just chalk this one up to bad luck. You got a lemon. Just like any piece of technology or machinery there are instances where it’s just got bad robot parts. Whether it’s a faulty sensor, transmitter, or receiver, it’s just junk. That’s okay tho! Dexcom has an incredible customer service and tech department that work, literally 24/7, to help you in the instance that something like this happens to you. They know how important their product is to your diabetes management and will ship you a new [insert broken Dexcom part here] overnight or 2-day air depending on the urgency.
2. Bad Insertion
Some people find that their dex is more accurate on certain parts of their body than others. This could be for a few reasons including how close to a muscle the sensor is, the quality of interstitial fluid in that area, or the amount of scar tissue in that area. The longer you have the Dexcom the more you’ll learn which parts of your body work the best.
3. Sliding In and Out
Check your site. Is the bandage lifting up or coming loose? If it is, that’s probably why your readings are off. Every time that sensor slides in and out of your body, due to the adhesive coming loose, it has the potential to throw of your readings. Key work here being potential. Sometimes half my bandage is hanging off and half the sensor is out and I have great readings. Sometimes I’ll just notice a little lift and my readings are totally off. If this happens to you it’s an easy fix: tape that sucker down!
4. Too Close to a Muscle
Typically when the sensor is too close to a muscle or near the fascia layer surrounding a muscle it will give you erratic readings (usually a false low). For me, this is especially true when I sleep on it AKA compression low.
5. Compression Low
I’m a side sleeper, so when my dex is on the outside of my leg or arm you bet I’m being woken up in the middle of the night from a compression low. A compression low is when your Dexcom is compressed, usually pushing close to a muscle, and giving you a false reading of a low. If this happens, roll over and sleep on the other side and you dex will balance back out.
Dehydration affects the circulation in your interstitial fluid big time; which is the fluid that the sensor reads. So if you’re getting wonky readings, try hydrating yourself.
Exercising can TEMPORARILY throw off your readings because the glucose in that particular area (where your dex is) might be burning off more glucose than the general circulation. Especially if your Dexcom is on your quad and it’s leg day, for example.
8. It’s too Close To Your Pump
The interstitial fluids in an area where insulin is being delivered will be different than the general circulation. This is why Dexcom recommends not putting your dex too close to your insulin pump, or injection site. However, I myself have never experienced this, and sometimes my two robots are just an inch away from each other. But, if this happens to you and you’re getting weird readings, just add some space next time.
Certain medications mess with your interstitial fluids, which is the fluid your dexcom reads.
Acetaminophen (Tylenol) or any drug containing paracetamol for example are notorious for causing false highs. If this happens to you, ignore your sensor readings for the next 8-10 hours and just use finger sticks (blood readings).
10. Roller Coaster BG
If I’m having a particularly bad BG day and my sugar is all over the place you can bet my Dexcom will be off for at least few hours. This is because interstitial fluids naturally lag 5 minutes behind blood sugar… you try keeping up with roller coaster moving that fast! If this is happening to you just know that your dex will catch up once your BG takes a chill pill.
11. Bad Calibration
There are a few rules to calibrating your dex if you want to get the most accurate readings.
- Make sure you have clean fingers! Giving your Dexcom a false BG reading because you had donut crumbs still on your finger will single-handedly destroy your readings for the next 12 hours.
- Don’t calibrate with straight up or straight down arrows. These arrows indicate rapidly changing Dexcom readings. Calibrating at these times will throw off the calibration algorithm built into the dex. If the Dex asks you to calibrate when you have an arrow straight up or down, wait until your BG levels out a bit and the arrows are gone. A diagonal pointing arrow is fine to calibrate with.
- Don’t calibrate when below 40 mg/dL or above 400 mg/dL. If the Dex asks you to calibrate at one of these times, wait until your BG get’s into range.
12. Over Calibrating
I learned this one the hard way. Calibrating more often than asked (by the blood drop) will not make your Dexcom more accurate; it will do the exact opposite and likely worsen the accuracy. The only time I calibrate, other than when asked to, is when my dex and blood sugar reading is more than 80 mg/dL off.
The Five Percent
Don’t let these 12 reasons make you think the dex isn’t a capable CGM, because it is. Many CMG users prefer the Dexcom over other CGM for it’s accuracy alone! In my experience, the Dexcom is extremely accurate. 95% of the time when I check my BG, the Dexcom is within a 20 mg/dL range. And if it isn’t, run down this list and you’re bound to fix it.
Question of the day
Have you noticed another reason for inaccuracies? Or do you have tips/tricks that help with accuracy? Let me know in the comments below!