A few weeks ago, an allergist prescribed a two-week course of an oral steroid to clear up my sinus inflammation. Before I take any new medications, I research them, first through a generative AI tool and then visit well-respected medical sites to verify the information.
I soon learned that this medication could significantly increase blood sugar. Even though I’ve always had normal A1C levels (a blood test that measures average blood sugar level over the past three months) I was concerned, so I contacted another doctor who recommended that I monitor my blood glucose while on the medication.
He suggested several ways to do that. The least invasive, but most expensive, was to use a continuous glucose monitor (CGM) that is like a patch, typically worn on the upper arm. He prescribed a Freestyle Libre from Abbott, which I wore for two weeks. They’re not cheap, and my insurance only covers them for people on insulin. Using a GoodRX coupon, you can get two 15-day devices for about $150. That’s $1,800 a year for those who need one full time.
The drug did raise my blood sugar, but it was reassuring to know that it was well within safe limits.
CGMs typically connect to a smartphone via Bluetooth and measure glucose levels in the interstitial fluid just under your skin. “This means there may be a few minutes delay in your CGM sensor glucose readings compared with fingerstick (manual) blood glucose readings,” according to Cleveland Clinic.
Over-the-counter monitors
I was fascinated by the information and wondered whether CGM monitors are available for people who are curious but don’t necessarily have a medical justification for a doctor’s prescription.
There are at least two approved over-the-counter glucose monitors. Lingo is from Abbott, and Stelo comes from Dexcom.
I reached out to Dexcom, which sent me a two-pack of Stelo CGMs to try over a 30-day period. Dexcom’s website says that the Stelo is “For people NOT on insulin, ages 18 years and older” and that it should not be used “if on insulin, on dialysis, or if you have problematic hypoglycemia.”
Like the Freestyle Libre, Stelo is easy to install and completely painless. Stelo comes in an applicator that you unscrew and press against your arm and press a button to apply. The hardest part is applying a protective cover over it to ensure it won’t come loose. Search “Stelo instructions” for a video explanation.
Other than the forementioned exceptions, anyone can use an over-the-counter CGM, including those who are just curious about the impact of food, exercise, stress, sleep and other factors. Stelo costs $99 for two 15-day devices, or you can subscribe for $89 a month. Because it’s non-prescription, you could share the two-pack with another person and each get 15 days of data, which is enough to get a sense of how different foods and physical activity affect you.
Reports every 15 minutes
Unlike prescription CGMs, Stelo only reports every 15-minutes. I was disappointed at first but soon realized that it was better than obsessively looking for changes as I ate and exercised. It still provides useful information, including trends, spikes and your glucose history in 5-minute intervals. “We want the data to be delivered to people in a way that they make changes when they need to and that the data is meaningful,” said Dr. Thomas Grace, Dexcom’s head of advocacy and outcomes
The app has a pre-set target range of 70 to 140, but you can set your own target. It shows your history but doesn’t allow you to print out detailed reports like the Freestyle Libre. Still, you could send screenshots to your doctor if you need help interpreting the results.
Paradoxes and spikes
There can even be some surprises, such as a paradoxical increase in glucose during exercise. According to Grace, “when we’re physically active, especially when we have high intensity physical activity, that actually is adrenaline that drives an adrenaline response by our body. And in response to that, we dump a little sugar into our bloodstream.”
Grace assured me that occasional spikes, especially after eating, are not necessarily an indication of health problems but said “If they’re persistently running higher than 180, that would be a good indicator to reach out,” to a medical provider.
You can listen to my full interview with Dr. Grace at connectsafely.org/cgm.
Sugary snack raised my blood sugar
I experimented by looking at my blood sugar level and then eating a sugary snack. A half hour later, it was up by 27 mg/DL, but after 20 minutes of light exercise, it was back down to where it was before the snack. My experience monitoring my glucose after meals, gave credence to a 2013 New York Times article that said, “a post-meal walk, as short as 15 minutes, can in fact help with digestion and improve blood sugar levels.”
As with all consumer medical, fitness and sleep tracking devices, it’s important to consult a health care professional before taking any action based on the data. It’s also important to not allow the device to contribute to your stress level, which can impact blood sugar, blood pressure, sleep quality and other metrics. I have a tendency to overreact to what appear to be abnormalities in reports, which is why I’m grateful to know doctors who can interpret them and usually reassure me that I’m OK.
Larry Magid is a tech journalist and internet safety activist. Contact him at larry@larrymagid.com.