In my last post, I recommended using a continuous glucose monitor, and then hours later, we experienced our first false alarm, meh!

Right around 1:30am this morning, the first alarm wakes me up and warns that my mom’s blood sugar is low. I bring her a peanut butter sandwich. She tells me that she had just finished snacking on a cookie and her blood sugar was in the 100s a few seconds ago. She eats half of the sandwich anyway and drinks some Glucerna.
A few minutes later the Libre app adjusts and corrects her glucose numbers.


I asked ChatGPT about it and this is what it said…
1. It measures interstitial fluid, not blood
The sensor reads glucose in the fluid between cells, which lags behind blood glucose by ~5–15 minutes.
If glucose is rising or falling quickly, you can see brief dips or spikes that don’t last. The algorithm may briefly interpret a downward trend, then correct itself.
This is the #1 reason for quick flip-flops.
2. Compression lows (very common)
If pressure is on the sensor—like:
Lying on it Leaning against a chair or armrest Tight clothing or a BP cuff
Blood flow around the sensor drops → the reading can suddenly look low, then pop back up once pressure is relieved.
3. Algorithm smoothing & recalculation
Libre 3 Plus updates every minute, but it also:
Uses recent readings to predict trends Recalculates when new data comes in
So you might see:
Minute 1: “Hmm, looks low” Minute 2: “Okay, nope—false alarm”
Especially common when glucose is hovering near a threshold.
4. Sensor settling or aging
First 24 hours after applying a new sensor = more noise Last day or two before expiration can also be jumpy
This doesn’t mean it’s broken—just less stable.
5. Hydration & circulation
Dehydration, poor circulation, or illness (very relevant during chemo, infections, or hospital stays) can make readings fluctuate more than usual.
Now we know 😑 My mom was already annoyed with the beeping, false alarms are definitely not helping matters. 😳 I am still a fan, even if it erroneously interrupted my sleep this morning.





