Just started Dexcom G6 - all readings incorrect

Bacon Cheeseburger soup

If you live somewhere cold, you can’t tell me this doesn’t sound like great comfort food :yum:

Just over 3 grams of carbs per serving

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Sounds exquisite except for the saturated fats I am trying to avoid these days. Those are probably what makes this taste soooo good.

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Well this is just unbelieveable. I contacted Dexcom because after over a week the overpatches did not arrive. We also had to go to the endo office to pick up some for my remaining sensors. Dexcom refused to overnight them and said that USPS takes up to 16 business days. I believe they were sent on a Friday which means they would take A MONTH to arrive. And they are an essential part of putting the sensor on your body so why would they not even include them with the sensors to begin with? So I am going to use the very helpful advice given by @CJ114 and purchase the OpSite on Amazon and also the skintac. I will make my own overpatches and keep them in place using the skintac on the edges.

The advice and help you all are giving me is just invaluable.

I am disappointed in the Dexcom, first because they overstate that it eliminates fingersticks in their advertisements but then in the fine print say you have to fingerstick for dosing, contradicting their advertising. Also after 14 days it has not found any “patterns” in my readings even though the overlay shows a daily pattern. The summary information it gives me about what would be considered my equivalent A1C and my percentage “in range” are way better than my last A1C and what my fingersticks are telling me. If you go by that data I am already hitting the goal, which is very far from the reality. So I am wondering if I even want to get another set of sensors and run out the transmitter life or just bag it.


Some people need skintac and others never do. I have never had to use skintac so don’t keep it around as that is just an extra item for me to worry about. Diabetics do not need any extra worries!!! The secret for me has been to shave the area where the sensor goes and then take a shower, dry area with a hair blow dryer and apply the sensor. During many months of the year I Inline skate 25-30 miles on nice days and when it gets really hot can get pretty sweaty and still don’t need the skintac. If I really need extra firm adhesion, I make an under patch first with OpSite and place on skin, put the sensor on the under patch and then make an over patch to go over the transmitter. I rarely needed that much adhesion, but that worked the best without any additional products such as skintac. Each person needs to find what works best for them.

@Marie20 Hi I have some questions. How can you wear a sensor longer than 10 days (is it a different brand than the G6?) - my receiver is telling me that my sensor session is going to end because it is at the end of the 10 day period.

Do you put the Skin Tac on the adhesive that is on the Dexcom sensor applicator after you peel off the two strips that protect the adhesive? Or did you mean that you put the Skin Tac on the overpatch adhesive? If I make my own overpatches with the product that @CJ114 recommended do I put the Skin Tac on that before I apply them over the sensor, or just if the edges peel, and will the Skin Tac work with that product too? We will go to the drugstore tonight to try to find the Skin Tac and I will first test it on my skin to make sure it does not irritate my skin.

You are supposed to only wear it 10 days, but I find it very accurate to wear it as long as possible until it goes wacky. That’s usually about 26 days for me, the longest being 38 days.

But it’s a hack people have figured it out. Dexcom keeps trying to stop it but so far someone keeps figuring out how to keep doing it. It can be really easy but it depends on your transmitter number. The latest transmitters require you to take out the transmiiter for at least 30 minutes and then restarting.

Easy way with older transmitters, doesn’t work a lot now though

Newer method working well.

I don’t use an overpatch, they didn’t work well for me, they came off right away. And once I used the Skin Tac it worked so well there was no need to use or try to use an overpatch.

This is what I do

  1. Unpeel white paper from sensor
  2. Apply Skin Tac all over the adhesive on the sensor making sure to get to the edges, but avoid the middle area that’s outlined that has the filament
  3. Put the sensor loader on the skin gently without pushing on it, hit the button without pushing into skin. If you push it will crumple the adhesive
  4. Let it set just a little bit to make sure it is adhering to skin
  5. Run your finger on top of the adhesive to make sure it is nice and flat and adhering to your skin
  6. If you applied a lot of Skin Tac you might want to hold it on for a few seconds to make sure it’s drying and adhering okay
  7. once the adhesive is nicely dry insert the transmitter

Then I touch up when it starts to peel up under the edges with a Q tip and more Skin Tac, making sure I try to only put the extra Skin Tac under the edges


just a plus one on the Alcohol Prep and SkinTac combo, although I’m currently using the 14-day Libre. Using it directly on skin, not leave any clear spot - just daubing a circle the size of my sensor. Used to knock them off regularly from the back of my upper arm (because I’m broad shouldered and tend to knock into door jams) trying other things and the SkinTac has been a savior.

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I have had very good correlation with my dexcom.
I wear it on my arms.
I check it with a finger stick now and again but usually don’t have to. It is pretty spot on.
You might want to check your meter to be sure you are calibrating to the correct readings.
They sell meter check solutions at the pharmacy. A low 60 and a high 200. Then you will get an idea how well it is performing.

Are you supposed to calibrate if it’s within 20% or outside 20%. 20% can make a difference between perfectly in range and being in hypo state and the alarms blaring.

So far my readings are roughly 36 mg (2mmol) different. Slightly outside the 20% for some readings. I’m finding its trending in the right direction (so moves with my BG rises and drops) but the discrepancy is enough for me to turn off my basal iq.

My DE says avoid calibration was the instruction given to her from tandem reps.

Just to prove my point it’s 1 am and my alerts are going crazy. The sensor reading is 3.4 mmol (61mg) and my meter reading is sitting nicely at 4.9mmol (88mg). I had to get up to get something to eat even though I’m in a good place just so the the sensor reading creeps back above the line and the alerts can be quiet so I can sleep! Grrrrr…

I’ve had my sensor on for around 40 hours. Is it time to call support?

I refuse to treat a phantom hypo with carbs just to silent a false alarm, but that’s me and I’m not using a Tandem pump as my Dexcom receiver. In your situation, I would use 1.1 mmol/L (20 mg/dL) to calibrate and then turn off the audible alarms, if possible. Is there any way for you to quiet the non-urgent low (55) alarms with the Tandem pump?

I find that the G6 does not like any calibrations that attempt to make a large correction. If I keep it to a maximum of 20 mg/dL (1.1 mmol/L) and maybe do two calibrations to step the sensor number up to a correct value. It’s more of a nudge tactic than a jump one.

Since the G6 sensor is notorious for first-day inaccuracy, I’ve taken to inserting my sensor 12-24 hours before I mount the transmitter and start a new session. In this situation, the best time to start a new session is in the morning so that any inaccuracy drama occurs during non-sleep daylight hours.

If I was faced with a pump that wouldn’t let me sleep due to repeated false alarms, I would be tempted to turn the pump off and replace the missing insulin with Regular or NPH.

This is a more drastic solution and would require some personal testing to determine safe doses for you. You could simulate this by doing it during the day so that you could monitor closely to observe what happens. One added benefit of trying this is that it will give you a basic tool to use when your pump fails. It’s survival education.

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I have no idea why some people refuse to calibrate. I calibrate when necessary and it behaves beautifully after that. You just have to make sure you’re in range and flat lined (BG, not EKG!) when you do so.


In this case I would just calibrate it, following Dexcoms 20/20 rule.
Possibly do another finger bg check based on symptoms if feeling it is lower.


Based on the sensor reading of 3.4 mmol (61mg) that’s considered urgent , so to my knowledge cannot be silenced below 3.9mmol (70mg). This is annoying when it’s a false alarm. I’ve acknowledged the alarm on the pump but I’m actually not sure whether it will continue beeping if my sugar doesn’t rise after the acknowledgment. Does anyone know?

I must say the dexcom sensor is already far better than the Medtronic. Although I still haven’t achieved accuracy, the direction of BG seems correct. It also feels a lot more comfortable and has very little pain. Just wish the accuracy will snap into place.

I’m actually not sure but my DE said that was the training she got. I read somewhere that the calibration mucks up the algorithm on the sensor. But if it’s not accurate in the first place I don’t see what can go wrong? Perhaps affect the sensor life? I don’t know

When I calibrate it always reverts back to the same level.
So I stopped calibrating. Generally if it’s out of range it’s a bad sensor. Generally my dexcom is very close to my finger sticks. So I don’t test much.

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Dexcom specifically describes when to calibrate.

Over-calibration can “muck up” the algorithm.


thanks, I may give that a go. Do you know whether there is a cap on the range difference. For example, if the meter says 100mg but your sensor says 200mg, thats a massive difference, do you calibrate? When I was on medtronic cgms, this was a big don’t calibrate until the gap is much closer.

I wonder why they don’t have a mmol version of this rule published anywhere. I tried to look for it but cannot find it. I’ve converted it into mmol below. I think the same rule still applies in mmol. But the 20/20 name doesn’t really make sense when it’s in mmols :sweat_smile:

The 20 rule says - Dexcom G6 reading must be within:
    • 20% of the meter value when the meter value is 4.4mmol (80 mg/dL) or higher
    • 1.1 mmol (20 mg/dL) of the meter value when the meter value is under 4.4mmol (80 mg/dL)

I appreciate Dexcom’s advice on calibration, but some of that is never going to happen. I use an semi-closed system with my G6. I’m literally trusting my life to it. I DEMAND accuracy, and have never seen this “mucked up” algorithm by doing it. You just have to do it at the right time, then no problem. 20 points variation if my fingerstick is under 80 is not going to cut it. If my Dexcom reads out of range, when I’m really not, you better believe I’m going to calibrate.

The only time I’ve ever had trouble calibrating is after a restart, when there’s a massive difference. I just did a second restart the other day (currently in day 22), fingerstick was a nice, round 100, but Dex read 240. I I always have to divide those giant restart leaps in several different calibrations. I tried to calibrate to 190, but the Dex rejected the calibration. My pump told me to try again in 15 minutes. It also rejected the 2nd calibration (sugar had changed by then, but I kept the 50 mg/dl difference). By the time I entered the 3rd requested calibration, it finally accepted it and has been running great ever since. It took me a little longer than usual to get it fully aligned with my real numbers, but no problem at all ever since. I check at least once a day on days 20-30, more often if I see the raw data going erratic, and until the very end of the sensor life the calibrations work.

I will say that I use one of the highest ranking meters, though. The Freestyle lite. It’s either 2nd or 3rd place after the contour next in terms of accuracy, but does exceptionally well in the target range. I definitely wouldn’t recommend using a random number generator, like the One Touch meters I detest so much, for calibrating, though.

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Yes this can be quite a massive interpretation if you are close to the hypo mark.

At 80mg (4.4mmol) I’m still functional and normal. At 60mg (3.3 mmol), i will feel symptoms of hypo and probably be freaking out about getting some sugar into my system. If the sensor tells me i’m at 60mg when I’m at 80mg, I say damn you sensor and shut up with your alarms already :grin:. …which is pretty much what happened yesterday at 1am when the alerts woke me up.

I used to do this on the medtronic - slowly tricking the sensor closer to the number. But the medtronic sensor dies (like completely stops working and a message tells you to replace it) if you have 3 calibration errors in a row. Is there a similar thing on the dexcom?