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Diabetes Technology: 20 years of continuous glucose monitor innovation (CGM part 1)
- Katlyn Agosta, MSN, APRN, FNP-C, CDCES
- Dec 12
- 11 min read
If you’re curious about continuous glucose monitoring (CGM), start here. My first CGM came with wires, a shower bag necklace, and zero real-time data. Fast-forward to 2025: tiny wearable sensors that can predict trends and prevent lows. Here’s everything that changed along the way. Florida health insurance 2026 alternative
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Ever wonder if continuous glucose monitoring (CGM) technology is right for you?
Hi, I'm Katlyn. I've been living with type 1 diabetes since 2002. I'm also a diabetes care and education specialist and nurse practitioner at Papaya Primary Care in Valrico Florida.
Part 1 of this CGM blog series takes you through my personal two-decade CGM journey—from my very first sensor to the technology we have today. My hope is for this story to shed light on the unique struggles people with diabetes navigate every day, while sparking empathy, awareness, and reassurance for anyone who feels overwhelmed.
If you’re struggling, please hear this clearly:
You are not alone.
Why CGM Matters (and What the Research Shows)
Over the past decade, real-time continuous glucose monitoring (CGM) has been a game changer for people with diabetes, myself included. Research shows:
Increased quality of life
Modest A1C reduction
Better time in range
Fewer low blood sugar episodes
Less glucose variability (aka “the roller coaster” that drives inflammation and long-term complications)
The strongest evidence is for people with type 1 diabetes, but growing research supports CGM use for those with type 2 diabetes—including those on oral medications alone.
Definitions for Common Terms (Click to Expand)
Time In Range (TIR):
The percentage of time your sensor glucose readings stay within a specific target range, usually 70-180 mg/dL for most people. The ADA suggested goal: at least 70% of readings within this target—that's about 17 hours per day.
Glucose Variability (GV):
The degree and frequency of sensor glucose swings up and down throughout the day. This is shown as the relative size of your glucose swings compared to your average glucose level as a percentage called Coefficient of Variation (%CV). A smaller %CV means your glucose levels are stable; a larger %CV means greater variability. The general target is less than 36%.
A1C (also called Hemoglobin A1c or HbA1c):
This is a blood test that shows average sugar levels over the past 2-3 months. How? By looking at the percent of sugar attached to the hemoglobin inside your red blood cells. For those with diabetes, an A1C less than 7% or sometimes 6.5% is considered ideal. Fun fact, A1C can be falsely lowered by certain health conditions including anemia, pregnancy, kidney/liver disease, and even after surgery from blood loss.
Low Blood Sugar (Hypoglycemia):
Low blood sugar, also called hypoglycemia, is when blood sugar levels drop too low to provide energy to the cells in your body. For people with diabetes, below 70 mg/dL is considered low. Severe low blood sugar is any number that requires emergency help from another person (think difficulty speaking, poor coordination, passing out, or even seizures because of dangerously low blood sugar).
Diabetes Quality of Life (DQoL):
Diabetes Quality of Life (DQoL) is a person with diabetes own perception of their well-being and impact of diabetes on daily living. This includes satisfaction with general life, treatment, physical and emotional health, diabetes impact, and worry/concerns about diabetes complications. The DQoL questionnaire is a tool often used in research or to guide holistic care beyond just blood sugar levels.
What Makes CGM So Powerful?
One word: awareness.
Awareness of patterns. Awareness of trends. Awareness of how food, movement, stress, sleep, medications, and even the weather can affect blood sugar.
Adam Brown (a fellow type 1 and author of Bright Spots & Landmines) is a big influencer and the type one community. He wrote an article about 42 factors that influence blood sugar (read it here).
The kicker? Many of these variables had opposite effects depending on the context. Take exercise for example, which can raise or lower glucose depending on timing, intensity, and medication.
I met Adam at a diabetes conference in 2018, he signed my copy of his book—a fun “type 1 in the wild” moment!
I’ll be honest though, early CGM technology wasn’t always as accurate or helpful as it is today.
A Look Back: The Start of My Diabetes Story
My type 1 diabetes journey began in August 2002, just after my 15th birthday. For six months I used insulin syringes to mix and inject Regular and NPH insulin twice daily.
My blood sugar was a roller coaster.
For reference:
Normal fasting blood sugar: 70-99 mg/dL
Normal blood sugar after meals: <140 mg/dL
I remember fingerstick checks in the school hallway before lunch and seeing numbers in the 260s or even 300s. On those days, I’d skip lunch (despite my growling stomach) and drink water, hoping to bring it down. Other days I’d have crashing lows without warning, thanks in part to the unpredictable “honeymoon phase,” where my pancreas would randomly dump extra insulin into my bloodstream.
A few early memories stick with me:
Sitting in an empty classroom, forcing down a yogurt to treat a low while a teacher scolded me for eating in a carpeted room.
Checking a blood sugar of 28 mg/dL in the back of our van and shakily telling my mom, “I’ll be fine,” as I worked to open my glucose tablets.
These moments were physically draining, emotionally exhausting, and honestly, dangerous.
Learning Modern Insulin Dosing (Circa 2003–2004)
At age 16 my family moved to a new state, which meant a new pediatric endocrinologist. She suggested insulin pump therapy. To prepare for the transition, I was switched to insulin pens for six months and learned how to use a carb ratio and insulin sensitivity factor. I carried a small calculator in my glucometer case because I’m terrible with math!
These newer insulins, Lantus and Novolog, were cutting-edge therapies back then. My first insulin pump did an even better job of mimicking natural insulin production, but it wasn’t a pancreas.
Even with better insulins and tighter dosing, I still struggled with erratic blood sugars, so I tested 10–14 times per day and gave frequent insulin doses to correct highs. Teenage hormones definitely didn’t help.
That’s when my first CGM experience happened.
My First CGM: The Blinded, Wired Era
At age 17, I wore a blinded CGM for three days. This technology was new to the market in 1999 (it was 2004 when I wore it) and silently collected and stored glucose data.
The sensor was inserted into my abdomen, and a wire connected the sensor to a portable battery pack. It was bulky and not waterproof. I had to place the device in a specially designed disposable halter (which was really just a plastic bag turned necklace) to protect the equipment in the shower.
I returned to the clinic, excited to finally get some answers to address my blood sugar swings and reveal patterns. Instead, I heard:
“There is no pattern. Keep doing what you’re doing.”
I was never shown the data.
I left discouraged, but still hopeful that one day CGM could become something meaningful.
Dexcom SEVEN PLUS: The Era of Frustration and Hope
Years later, at age 22, I eagerly unboxed the latest CGM technology: the Dexcom SEVEN PLUS (fun fact: the name was because it could be worn for 7 days, an increase in wear time from 3 days with the previous version, plus added enhancements like logging events and better reader display screen).
I was excited and nervous. I read the manual cover to cover (naturally), inserted the sensor, waited impatiently through the two-hour warm-up, and finally got my first reading:
Three question marks.
After the manual failed me, I finally called tech support: faulty sensor.
I tried again. Same process. This time it worked—but now it was midnight.
I celebrated my small victory and crawled into bed.
The first few weeks were full of discoveries.
Tylenol Caused False Highs
I remember hearing the song “Hey Soul Sister” by Train for the first time on the radio just before walking into the hospital for my clinical rotation. It was my last year of nursing school, and I had a nagging headache behind my eye. I chalked it up to dehydration and too much screen time, so I took a dose of Tylenol, and continued on.
Just as the edge lifted off my headache, I heard the high blood sugar alert. A glance at my CGM sent me into a panic with the word “HIGH” scrawled across the screen. The glucose dots were at the highest possible marking, indicating levels over 400. I remember thinking: That’s weird. I’m not even thirsty.
I checked a fingerstick: low 100s.
Checked again: same result.
Tech support confirmed that acetaminophen (Tylenol) could cause false highs. About four hours later, just as quickly as the sensor glucose spiked, it dropped back to target. I became an ibuprofen girl after that.
Out of curiosity, I reread the manual—there were no medication interaction warnings back then. They were added later.
Alerts Weren’t Loud Enough
I soon discovered this egg-shaped receiver was nowhere near loud enough to wake me, even at max volume. This didn’t surprise me; I once slept through an earthquake strong enough to knock books off shelves (for real!).
In theory, distinguishing the low alert with a lower tone and the high alert with a higher tone made logical sense. In reality, these soft hypoglycemia alerts were not effective.
My endocrinologist suggested putting the receiver into a glass cup with coins to amplify the alert. It helped, but I would still sleep through my new jingling alarm for more than an hour before waking up to treat the low.
Accuracy Was Hit or Miss
The discrepancy between fingerstick and CGM values was often big and incredibly frustrating. One day, I ripped off my sensor, threw it and the receiver into a box, and shoved everything into my closet. It sat there untouched for two months.
Eventually, I tried again.
Dexcom G4: Accuracy Sparks a Movement of DIY Innovators
With the Dexcom G4 came better accuracy and a slimmer, rectangular receiver. This receiver included an alert option called “hyporepeat,” which provided an absurdly loud low alert and repeated every five seconds. Perfect for me.
A quick glance at my CGM trend once every hour or so helped me proactively address blood sugar changes.
Sensors were changed every seven days, but the transmitter was reused on each sensor until the battery died three months later. The cash price for a replacement transmitter was around $300, so people started getting crafty.
A DIY movement began where people would try to replace the battery and extend the life of their transmitter to save money.
This process required carefully grinding away the plastic casing, removing the old battery, soldering a metal wire between the new battery and the transmitter, then resealing everything with epoxy in hopes of waterproofing the device.
This was definitely not an officially supported procedure, but it continued with the next generations of G5 and G6 transmitters with variable success rates.
Rebuilding transmitters was not within my skill set, but I was curious.
I once mailed an expired G6 transmitter to another type 1 in Canada. He mailed it back with the new battery and a beautiful sparkly teal epoxy top—my favorite color. It didn’t work, but I kept it as a conversation piece and reminder of the resilience required to thrive with diabetes.
Dexcom G5: Bluetooth Compatibility & Treatment Approval
With the Dexcom G5 came more improvements, better accuracy, and Bluetooth compatibility. Using my phone allowed for more customizable alert options, and ditching the receiver for a mobile app was liberating.
I already carried a cell phone and wore an insulin pump; eliminating one device was welcomed.
The G5 also revolutionized my routine with FDA approval to use CGM values to make treatment decisions.
I’ll admit, it took several months for me to fully trust the system, but I slowly went from 6–10 fingersticks per day down to once every 12 hours for CGM calibration.
Glucose Accuracy Leads to Insulin Automation
As CGM became more accurate, insulin pumps began using the data to automate insulin dosing. My first experience was the approval of Basal-IQ in the summer of 2018. My pump could now look 30 minutes into the future based on glucose trends, and slow or pause insulin to prevent or blunt low blood sugar events. How freaking cool is that?!
I remember thinking, “Sweet, but I don’t have that many lows.” I was surprised to see how often my insulin would pause—and even better, how it reduced the burden of diabetes just a little, quietly in the background. My box of fruit snacks (my preferred low blood sugar treatment still to this day) lasted a lot longer too.
Control-IQ came next in January 2020. This added the ability for insulin increases and correction boluses through the algorithm—without me needing to actively approve it. Finally, fasting blood sugar at goal… every. single. morning. This had a pleasant domino effect on the rest of the day as well, though pesky post meal sugar spikes are still an issue.
There are additional limitations on which settings can be adjusted while using the algorithm, so still not really a pancreas. I'm looking forward to what future systems will allow.
Dexcom G6 and G7: CGM Becomes Sophisticated (and Easy)
I upgraded to the Dexcom G6 in 2021. Technology advancements finally introduced acetaminophen-blocking, so no more false elevations from Tylenol.
The application device was redesigned, making new sensor application easier and less painful. I remember the first one I put on feeling like a quick tap from the pad of my finger.
With further improvements in accuracy, calibration requirements were removed completely. Setup was faster with a QR scanner, though I still had to manually enter the sensor code into my insulin pump.
Sensor wear time increased from seven to ten days, and I was able to reduce fingerstick testing to 2–4 times per month. The little black dots on my fingertips from 16 years of glucose testing finally disappeared.
Dexcom G7: Shrinking Size and Disposable Transmitters
On April 1, 2024 (for real!), I said goodbye to the G6 and hello to the much smaller G7 sensor.
For the first time, the entire device—including the transmitter—is disposable.
The applicator was redesigned again, even smaller now, and kept the QR code feature for pairing a new sensor to the phone app.
The warm-up time was reduced to only 30 minutes (compared to two hours with prior generations), and this generation now has a 12-hour grace period, which is a game changer at bedtime.
Dexcom G7 has recently been approved by the FDA for 15-day wear plus the 12-hour grace period, making it the longest wear time for disposable devices to date.
At this point, I feel naked without a CGM.
Head to Head: Dexcom G7 and Libre 3 Plus
In February 2025, I had the opportunity to trial the Dexcom G7 alongside the Freestyle Libre 3 Plus. Overall, in my experience, the devices were comparable. Of course, there are some minor differences between the two, but both are considered excellent options for glucose monitoring and are approved for insulin dosing.
Closing Thoughts
Two decades of diabetes technology have taught me this:
CGM isn’t just data—it’s awareness, clarity, and confidence.
Every advancement chips away at the burden of diabetes management, giving me more room to live life first, with diabetes a bit more on the backburner. Ironically, this technology helps me feel more human.
Stay tuned for Part 2 of this CGM blog series. We’ll compare and contrast the available CGM devices on the market today and outline factors to consider when choosing the right sensor for you.
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Author's Note
This story was written by me, Katlyn Agosta, MSN, APRN, FNP-C, CDCES—nurse practitioner, certified diabetes care and education specialist, and proud Valrico local. I started Papaya Primary Care to make healthcare more personal, accessable, and prevention focused again. My specialty is diabetes care, education, and empowerment—from the lens of my own type 1 diabetes experiences.
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