Hoping for some advice please. Kate (15) has started using the Freestyle Libre CGM about two months ago. I have been reading other posts about false lows and inaccurate readings with this particular CGM. Kate has been dipping low in the small hours of the morning. I check her at 1.30 and at 3am, but sometimes miss the lows. They seem to self correct. Is this right? Is it because some foodstuffs really take a long time to impact the glucose levels? I am finding it really scary, particularly when the sensor says she has been low (at about 2.3) for over an hour. We have halved her nightly basal units of Optisulin. Any ideas? Thank you. Wendy
I use the Dexcom g6, so I don’t know much about the specifics of the Libre, but I have noticed similar patterns overnight and my endo said it may be a result of “compression lows”–if I’m in a position that puts pressure on the sensor, it leads to false low readings (I don’t know exactly why). This may be what’s happening to your daughter. I don’t know for sure–there may be another explanation, and hopefully others on this site can offer some insight–but it’s one theory at least. 
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Hi Wendy @francesjean, I can understand your very legitimate concern when you see Kate’s glucose at 2.3 mmol/L [41 mg/dl] for over an hour.
If I was in your position [I personally have this happen to me], I would NOT blame it on false readings until I rule out other factors; it may be advisable that when you do her finger-sticks that you re-calibrate her Libre as long as you are certain her finger is clean.
Some possible solutions could be adding an additional before bed snack if her BGL is less than some level - such as less than 8.3 [150 mg/dl]; or, change the timing of her Optisulin.
Optisulin, a long-lasting glargine insulin, is not supposed to have peeks but it may have some effect like that on Kate. This is something that you and Kate should discuss with her medical team - I’m not a medical doctor but speak only from me similar experience.
Thanks, Abby. It seems logical that the compression lows may be affecting the readings. I am worried about how long those lows last. All the best
Thanks Dennis. The night time lows scare me, because Kate cannot “feel” them as she can when she is awake. I know you have had T1 for a long time - and I value the advice you give on this forum. I am puzzled about lows that go up without glucose being taken. My logic says that lows, left untreated, will go even lower. Please could you let me know if and how lows “self correct” Is that your experience? Thanks and regards
@francesjean Hi Wendy, notwithstanding a sensor error (as above) If you go low, your liver can dump a form of stored sugar called glycogen which will raise your blood sugar.
if your basal rate is not high enough, a low caused by a over correction or by an over bolus (because of a high guess on carbs) can go back up over time because the lack of basal will drive sugar back up.
finally a fatty mixed carb, or complex carb (take pizza) can cause a low because fast acting insulin acts too fast, and gets ahead of carb absorption (causes low) and then as the carbs absorb, your sugar comes back up again.
these can also happen in combinations
I sometimes “correct” a minor low by dropping my basal rate for an hour. it beats the heck out of drinking juice if I don’t need the calories.
if you are 39 mg/dl and dropping, these things will not help and it is the best move to go ahead with a fast carb like glucose. I only do the “reduced basal” trick when I am like 65ish and want to be 75mg/dl
good luck.
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@FrancesJean - The best way to “treat” compression lows, is to do a finger stick to check what the blood sugar is really doing. Don’t worry that the sensor reading is off. What really matters is where Kate’s BG really is! If you’re concerned she may actually be dropping, check her, wait 1/2 hour or so and check again. That way you’ll see what her blood sugar is doing so you can relax.
Pam K
T1D 54 1/2 yrs and counting!
Thank you Wendy @francesjean for your warming comment.
Pam @pamcklein makes a very positive advice by always double-checking with a finger-stick if there is any question. Day or night, if I awaken, if I don’t feel what my CGM is reading I always use a meter. But, as you said, Kate doesn’t recognize a “low” when she awakens.
@Joe wrote much better than I could toe explanation of how low BGL will correct itself. I’ve allowed mine to correct on its own except when very low or evenings following heavier than usual exercise - like last evening, or at times when I suspect “user error” such as over-correcting a high or miss-counting carbohydrates.
Thanks, Joe. That all makes sense, and was a very helpful reply to my question. Although Kate was diagnosed 4 years ago, she had a fear of wearable technology, so the whole CGM scene is new to us. I really appreciate the information and support on this forum. Many thanks
Thanks Pam. She hasn’t actually done any finger prick testing since she started wearing the CGM. I think maybe it is a good idea to do a few a week…
Thanks Dennis. All the best
My daughter wears the Dexcom 6
We get false lows at night/ early morning and some aren’t false however I set the alarm parameter a bit tighter so a low will trigger at 90. That alerts me to check things out. I always verify with a fingerstick regardless and lots of times it’s a false low and I can soundly return to bed. But on the rare instance it’s a true low … I will only treat off the co formed fingerstick.
Not convient at 3 am but it’s our way of verifying. We hold to this routine with highs and lows during the day as well. But honestly I only fingerstick maybe 2-3 times per 10 days when Dexcom is on
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I posted recently about false nighttime lows with my Freestyle Libre. They began suddenly, after having good accuracy for a few months. I’m still not completely sure, but it seems I had a couple of bad sensors. (I may have stored them too close to the heat vent for a few days!) Overall I like the Libre and it’s quite accurate for me. Abbott was helpful in sending me a replacement sensor, too, when I called them about my trouble. My false lows seem to have stopped…for now.
I did learn through this to always finger-stick before treating lows, especially at night. I use my Libre test strips for this, so the “real” BG number is stored along with the false low number. I can see it later on my Libreview reports.
Doing a finger-stick on a different meter helped me realize at first that my sensor readings were inaccurate. Comparing finger-stick readings between the Libre and my other meter helped me see the problem was with the sensor, not due to a bad reader or the lag time between blood and interstitial fluid.
Hope this helps! - Lisa
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