Anxiety and questions about Dexcom dropping fast

Hi, kinda sorta new here, not new to diabetes. Been type 2 for almost 20 years. Currently on 40 units of Lantus.

My anxiety and questions below:

I wear a dexcom g6, I never calibrate it, don’t have to. Last night at 830ish my Dexcom alerted of a low, below 80. All day long I had been running in the 200s. I looked at dexcom and it had dropped 200pts in an hour. I tested with my meter, it was 80, checked again, it was 66. So immediately have a panic attack and start treating. Shaking, sweating, heart pounding and an hour later I’m going back up, but becuz I freaked out, it went really high. I did calibrate my dex immediately after those first finger pokes.

So, today called dexcom, they said probably defective sensor. Ok, sending a replacement. Also called drs office asking if BS can drop that fast, they said yes, that can happen.

That can’t happen, can it? 200 pts that fast? It sounds like a dumb question but I guess I was so shocked thinking I was high. So now I don’t trust my dex even tho I’ve calibrated it a couple of times today. It seems to be spot on…now. I’m wearing the same one, didn’t replace it with a new one. And my anxiety is still through the roof. I’ll be setting alarms to finger poke tonight.

Any advice is much appreciated!

That can definitely happen with type 1, so I assume it can happen to anyone, or at least anyone taking insulin. Sometimes you want it to drop that quickly (ex: a blood sugar of 300 or more). It can be scary, but if you think too hard about anything diabetes related, it’s scary. At least sugar fixed your problem, and almost all the time, eaten sugar will be enough if you are awake. Maybe investing in some glucagon could give you peace of mind.

But also, sometimes sensors are wrong. I have been using the g6 for 6 or 7 months, and it’s almost always perfect, but 2 days ago, it told me I was 118, but I felt low. I tested and was 59, and the calibration with dexcom is not good in my opinion because it took 5 hours and 6 calibrations before the g6 got on the same page as my meter. But they did get on the same page and are in sync now. No technology is perfect, but in my opinion, it’s still better than testing 10 times a day and being in the dark the other 70 percent of the time.

I use G4, but if I used G6 I think I would still BG check 2-3 times per day. Then not calibrate if G6 is close. It may be less accurate the first day or so. For me, dehydration can lead to inaccurate G4 readings, so I make sure to drink plenty.

Did you have a normal meal before the low? We’re you more active ?
Since you take Lantus only, do you think it covers your evening meal? Or do you take oral meds with meals? If so, a skipped or smaller dinner, or exercise could have resulted in the drop at 8:30.

Hmmm, I wouldn’t think being a T2 on Lantus would cause such a large drop. What if BS was only at 100 and that large drop happened?

I will start spot checking.

Dehydration may be a possibility, more water is great advice. Dinner was large salad with chicken and carb items including croutons along with a bite of meatloaf. No to the activity. I really can’t put my finger on it. I try to keep my carbs low at dinner and have some kind of snack before bed, yogurt, cottage cheese, cheese and deli meat, I never skip meals.

A normal dose of Lantus would not drop a T2 220mg/dl in just an hour, unless … you had given yourself that dose a short time early (within 1-3hrs). I’ve been injecting 55 yrs, and on 2 or 3 occasions I’ve injected into blood vessels / capillaries that put the dose directly into bloodstream. The results are enormous blood glucose drops over a short period of time. Twice it put me into convulsions and I awoke in the ER. BTW, as always when I was MDI, drawing back did not pull any blood.

The other explanation (as @MM1 was suggesting) is your sensor was showing you a false 220, when you were actually closer or under 100.

Sometimes these things are never explained.

There is an additional Dexcom alert you can turn on.

Fall Rate --> 3 mg/dL/min or 2 mg/dL/min

3 mg/dL/min ==> 180 per hour or 15 every five minutes (ie - each cgm data point)
2 mg/dL/min ==> 120 per hour or 10 every five minutes (ie - each cgm data point)

Having this alarm turned on may give you additional comfort and let you know sooner?


I did inject the Lantus at 7:30 last night and yes, I’ve heard about directly injecting into the vessel. I never look to see if blood appears after. Definitely something to pay attention to.

I’ve spent the better part of today wondering what happened and checking my dex and finger sticks. I don’t want it to happen again. I just get so tired of dealing with it…I guess that’s for another thread.


Just discovered it today and it is turned on now. Thank you for the explanation!

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Sometimes I don’t take any insulin for food, and I drop all day, just munching on fruit to keep it up. The next day, I’m high all day while taking extra insulin and cutting back on carbs. I cant figure out why, but I’m betting it’s either hormones or stress. Its unpredictable. Nothing about this disease is predictable. Trying to take a logical approach doesn’t work because there is no logic, all you can do is try to relax because theres a 90 percent chance that you will never figure out what happened.

You’re totally right, diabetes is unpredictable. You mention stress, hormones, my A1c in November increased to over 7% for the first time in many years. Lots of stress at work, surgery in December and most recently a cold. I have an appointment to see my endo Wednesday. Thanks for the reminder. One day at a time!

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Yes you can drop 200 points in an hour. If I can, you can. :slight_smile:

Don’t calibrate a CGM when your bgs are moving rapidly. It’ll throw off the accuracy.


Thanks for the reminder about when to calibrate.

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When i got Toradol shots it caused a drastic drop in blood sugars, hours, maybe 8-12 hours later. It took me more than a few shots to realize it was being caused by the Toradol injection. But I remember dropping fast and my blood sugars did not want to climb back up easily. literally drinking 3 apple juices, candy etc trying to get it to rise. Of course about 2-4 hours later I was then in the 300’s . But that was a delay to go up from all the sugar I had!

That’s scary. Good thing you put the two together. I’ve been taking Lantus for quite a while, years. Yesterday I ran in the 200s, today closer to normal. I calibrated my dexcom twice today, first thing this morning and again just before dinner.

Interesting that you were approved for a CGM, given that you are only using Lantus.

If your graphs are not yo-yo like, and you aren’t having gaps in the data, it’s unlikely that the G6 is the issue. My son has the G6 and it has caught many lows, but there have been “compression lows” in the night, which are false readings, due to moving his body a certain way. G6 read 55, while finger poke read 164… Like President Bush said in hindsight, “Trust, but verify.” You verified, and found it was correct.

Heavy exercise can cause big drops a few hours later, especially at bedtime. I’ve gone from 340 to 50 in the night, after a day of rearranging my garage. I suspect that you did have a long day, and that 9PM is your normal bedtime?

I know from experience that I have to wash my hands after taking glucose tabs, since the powder floats everywhere. I went from 220 to 88 by washing my hands and retesting…

It also sounds like you over corrected after the low. When your heart is racing, it’s tempting for me to stuff a dozen tabs in your face to get it to stop. Reminds me of my wife cranking up the thermostat to 85 degrees, thinking the house will get warmer that much faster. As you probably already know that just doesn’t work.

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I’ve been using a CGM for a few years, never thought twice about possible issues not being approved. I hadn’t been using my dex5 because I was frustrated with failure, false readings, poor adherence. Then a couple of months ago I had a really severe low, that’s when I contacted my doc for the dex6. I’m happy to be using it again and have had few problems!

I’ve taken the advice of a few here and do a few calibrations during the day, first thing in the morning and one early afternoon and again before bed.

Over correcting? Yes, I always do. Trying to do better but it’s hard.

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I think Bee_Kay was referring to medical insurance approving a CGM. I agree, that’s very much outside the norm, but you didn’t mention how it was paid for.