Sunscreen, Sweat & Sensor Survival
How to keep your devices from quitting on you this summer From sunscreen sabotage to sweat-soaked adhesives, summer can be brutal on your T1D tech. This episode unpacks what really causes sensor dropout, plus tips to keep your gear stuck...
The episode, word for word
You ever get a CGM reading that says you're 172...
...but your body says "you're about to eat the floor"?
Or worse, you get a low alert that freaks out your spouse on the Follow app, but you're actually fine, watching Netflix and snacking on grapes?
Today's episode?
We're talking CGM accuracy, lag time, calibration, and why sometimes... your CGM is kinda gaslighting you.
This is Your Best T1D Year.
Here's the science-y breakdown:
CGMs don't read your blood sugar directly.
They measure interstitial fluid, the fluid between your cells.
It's basically the echo of your blood sugar levels. Which means there's always a little lag, about 5 to 15 minutes behind what's actually happening in your bloodstream.
That's why when your blood sugar drops fast, your CGM might still show you as steady.
Or when you eat a huge meal and spike hard, the graph looks like it's on a delay.
A 2023 report from the American Diabetes Association's CGM Accuracy Consensus Panel says that modern real-time CGMs have a MARD, that's Mean Absolute Relative Difference, of 7 to 13%.
Which means a reading of 100 could reasonably be anywhere from 87 to 113.
It's not perfect. It's a guide.
So when should you believe your CGM?
When your blood sugar is stable
When it matches how you feel
When it's been calibrated recently (if required)
And when should you double-check?
During rapid changes, like right after exercise, meals, or insulin
When you've been sleeping on the sensor (compression lows are real)
When your symptoms don't match the graph
When your CGM's being dramatic for attention
Yes, it happens. Especially after showers, site changes, or when you accidentally smack it on a doorframe. (Don't ask.)
Some CGMs don't need calibration. Others allow it.
But here's the rule: Don't calibrate during a spike or drop.
Calibrating during a rapid blood sugar swing can actually confuse your CGM even more.
The best times to calibrate?
First thing in the morning
Before bed
When your blood sugar has been stable for at least 20 minutes
And always wash your hands. Or use a clean site. Orange juice fingers are not a vibe.
I've gotta tell you, this happened to me.
During the Little Rock Half Marathon, my CGM said I was 172...
But I felt off. I was shaky, sweaty, not just from the run.
I checked with a fingerstick, and I was actually in the low 70s, about to hit a wall.
That moment reminded me:
Tech is a tool, not a truth.
It's smart to trust your instincts, even when the tech is chirping something different.
This week, practice checking in with yourself, not just your CGM.
If the data doesn't match your symptoms, pause and ask: "What's really going on here?"
And maybe do one fingerstick, just to reconnect.
DM me your weirdest CGM-inaccurate moment or tag me in a story where you called it before the sensor did.
If your CGM ever makes you feel like you're doing diabetes wrong...
Blue Circle Health is here to help.
They offer real coaching and medical care, for free, including CGM support, troubleshooting, and people who actually listen.
Sign up today at [ ](https://bluecirclehealth.org)
Next episode?
We're talking low-tech tracking strategies, because not everyone has a CGM, and some of us just need a simple system that doesn't feel like a NASA dashboard.
Until then,
You're not doing a bad job.
You're doing a difficult job.
And you're crushing it.
This is the script as read on the mic, lightly tidied for reading. Education, not medical advice. Talk to your care team before you change anything about your insulin.