What a CGM does, briefly
A continuous glucose monitor (CGM) is a small wearable sensor that measures interstitial glucose — the glucose in the fluid between cells, which closely tracks blood glucose with a small lag. The sensor is applied to the back of the upper arm and worn for between 10 and 15 days depending on the model. Readings are sent to a smartphone app every minute or every few minutes, producing a continuous trace of how your glucose is moving in response to meals, exercise, sleep, and stress.
Until a few years ago, CGMs were almost exclusively used by people with type 1 diabetes managing insulin in real time. That has changed quickly. In 2024 the FDA cleared the first over-the-counter CGMs in the United States, and these consumer-focused sensors are now widely used by people with type 2 diabetes, prediabetes, or simply by adults who want to understand how their own bodies respond to food.
Quick comparison
| Dexcom G7 | FreeStyle Libre 3 | Stelo | Lingo | |
|---|---|---|---|---|
| Manufacturer | Dexcom | Abbott | Dexcom | Abbott |
| Category | Prescription, clinical | Prescription, clinical | Over-the-counter, wellness | Over-the-counter, wellness |
| Wear time | 10 days + 12-hour grace | 14 days | 15 days | 14 days |
| Warmup | 30 minutes | 60 minutes | 30 minutes | About 1 hour |
| Reading frequency | Every 5 minutes | Every minute | Every 15 minutes | Every minute |
| Calibration required | No | No | No | No |
| Real-time alerts | Yes (high / low / urgent low) | Yes (high / low) | No | No |
| Prescription required | Yes | Yes | No (US) | No (US) |
| Availability | US & Canada | US & Canada | US (OTC) | US & UK (OTC) |
| Best suited to | People managing insulin | Insulin users or detailed self-trackers | Prediabetes, T2D not on insulin | Wellness / metabolic self-tracking |
The most important thing to understand about this comparison is that these products are not really competing for the same buyer. They are aimed at different use cases — prescription clinical devices for insulin users, and lower-cost over-the-counter sensors for everyone else — and the right choice depends entirely on which group describes you.
The prescription CGMs
Dexcom G7
The Dexcom G7 is the latest generation of what is widely considered the most clinically capable consumer CGM. It is the model most commonly prescribed for people with type 1 diabetes, and it integrates with most major insulin pumps. The sensor is roughly 60 percent smaller than the previous generation and warms up in 30 minutes — meaningfully faster than the two-hour warmup of older Dexcom models.
Where the G7 stands apart is its alert system. It is the only device here with a dedicated "urgent low" alarm that sounds even when the phone is silenced, which matters enormously if you take insulin. Reported accuracy (MARD, mean absolute relative difference) sits around 8 percent, among the best on the market.
The trade-off is access. In both the US and Canada the G7 requires a prescription, sits at the higher end of the price range, and is most cost-effective when covered by insurance. For people not managing insulin, much of what makes the G7 superior — pump integration, urgent low alarms, the tightest accuracy — is irrelevant in daily use.
STRENGTHS
- Highest reported accuracy of the group
- Urgent low alarm overrides silent mode
- Insulin pump integration
- 30-minute warmup
- Reliable real-time data delivery
LIMITATIONS
- Prescription required (US & Canada)
- Higher price point
- 10-day wear shorter than competitors
- Most clinical features unnecessary for non-insulin users
FreeStyle Libre 3
The FreeStyle Libre 3 is Abbott's third-generation consumer CGM and the direct competitor to the Dexcom G7 in the prescription market. The defining technical difference is reading frequency — Libre 3 sends a glucose value every minute, compared to every five minutes for the G7. For most users this is academic, but for anyone studying their own data closely (exact peak times, comparing meal responses), the higher resolution is genuinely useful.
The sensor itself is the smallest on this list — about the size of two stacked coins — which many users find more comfortable for 14-day wear. Reported accuracy (MARD around 7–9 percent) is comparable to the G7. The Libre 3 also offers high and low alerts, although the alarm system is generally considered less robust than the G7 for people who depend on it for insulin safety.
Where the Libre 3 lands well is the combination of long wear time, high reading frequency, and a lower price point relative to the G7 in most markets. It is the prescription CGM I most often see recommended for people who want clinical-grade data without needing pump integration. A practical note for Canadian readers: Abbott's FreeStyle Libre line has long been sold through pharmacies in Canada and many other countries, sometimes without the prescription hurdle seen in the US — worth checking with your local pharmacy.
STRENGTHS
- 14-day wear (longest of the prescription CGMs)
- Reading every minute
- Smallest, thinnest sensor
- Generally more affordable than G7
- Strong companion app
LIMITATIONS
- Prescription required (US)
- 60-minute warmup (longer than G7 and Stelo)
- Alarm system less robust than G7
- Limited insulin pump integration
The over-the-counter CGMs
Stelo
Stelo is Dexcom's answer to a different question. Rather than competing with the G7 in the clinical market, Stelo was designed from the ground up as an over-the-counter, wellness-focused CGM for adults not on insulin — people with type 2 diabetes managing through lifestyle, people with prediabetes, and adults using a CGM purely to learn how their bodies respond to food.
The hardware is built on the same biosensor technology as the G7, but the experience is deliberately different. Stelo reports a glucose value every 15 minutes rather than every minute or five, and there are no real-time low or high alarms. The companion app focuses on patterns, trends, and meal-timing insights rather than the moment-to-moment stream an insulin user needs.
For the use case it was built for, Stelo is excellent. The 15-day wear is the longest on this list. In the US it is sold direct-to-consumer without a prescription — typically a two-sensor pack for around $99, or a monthly subscription near $89 — and is available online, including through Amazon. For someone whose goal is "I want to understand which foods spike my blood sugar," Stelo delivers exactly that with minimal friction. It is a US product for now; it is not yet available in Canada.
STRENGTHS
- No prescription required (US)
- 15-day wear (longest here)
- Direct-to-consumer subscription model
- Built specifically for non-insulin wellness use
- Same proven sensor platform as the G7
LIMITATIONS
- No real-time low or high alarms
- 15-minute reading frequency
- Not suitable for people on insulin
- Not yet available in Canada
- No insulin pump integration
Lingo
Lingo is Abbott's over-the-counter entry, launched in the US alongside the first wave of OTC sensors and also sold in the UK. It is built on the same FreeStyle Libre platform that powers Abbott's prescription CGMs, but the app and positioning are different: Lingo is marketed as a metabolic-wellness tool — pitched as much at people without diabetes who want to understand how food, exercise, sleep, and stress move their glucose, as at people managing type 2 through lifestyle. It is for adults 18 and over who are not on insulin.
Practically, the sensor is worn on the back of the upper arm for 14 days and reads frequently (close to once a minute, like its Libre sibling). Pricing is flexible and modular: roughly $49 for a single two-week sensor, $89 for two, or about $249 for a six-pack, and it is now stocked in major retail as well as online. Like Stelo, it has no real-time alarms and is not for insulin users. One thing to check before buying: the Lingo app launched iPhone-first, so confirm current Android support if that matters to you.
A point worth knowing if you specifically have type 2 diabetes: Abbott also received FDA clearance for Libre Rio, an over-the-counter sensor designed specifically for adults with type 2 diabetes not on insulin (rather than Lingo's general-wellness framing). It has been rolling out, so if you want an OTC option built around diabetes rather than wellness, it is the one to look for.
STRENGTHS
- No prescription required (US)
- Built on Abbott's proven Libre platform
- Frequent readings (about every minute)
- Flexible pricing, including a low-commitment single sensor
- Coaching and insights aimed at habit change
LIMITATIONS
- No real-time low or high alarms
- Wellness framing — Libre Rio is the diabetes-specific sibling
- Not suitable for people on insulin
- iPhone-first at launch — check current Android support
- US & UK for now; not yet in Canada
One to watch: the Accu-Chek SmartGuide
Accu-Chek SmartGuide (Roche)
The SmartGuide is Roche's return to continuous monitoring, and its distinguishing feature is prediction. Beyond showing your current glucose every five minutes over a 14-day, water-resistant sensor, its companion "Predict" app uses AI to flag the risk of a low in the next 30 minutes, forecast where your glucose is heading over the next two hours, and estimate your risk of a night-time low before you go to bed. Reported accuracy is strong, with a MARD around 9 percent.
Two honest caveats. First, unlike every other sensor on this page, the SmartGuide requires calibration (occasional fingersticks as prompted by the app), where the Dexcom and Abbott sensors are factory-calibrated. Second, it is indicated for adults with type 1 or type 2 diabetes on flexible insulin therapy — and its standout predictive features matter most to people at genuine risk of lows, which generally means insulin or sulfonylurea users. For a newly diagnosed type 2 reader using a CGM mainly to learn how food affects them, a simpler factory-calibrated OTC sensor is usually the better starting point.
I'm testing a SmartGuide myself where it is sold, and I will publish a hands-on review once I have worn it through a few sensor cycles. (For the record: PureNovus has no relationship with Roche — this is independent coverage.) If you are an insulin user who fears overnight lows, this is the device worth keeping an eye on as it works toward North American approval.
Which one is right for you?
If you are managing insulin, the choice is between Dexcom G7 and FreeStyle Libre 3. Get the prescription — the clinical features matter for you, and the cost is usually offset by insurance. The decision between them typically comes down to whether you use an insulin pump (favouring G7) and which app you prefer.
If you have type 2 diabetes managed through lifestyle, prediabetes, or you are simply curious how your body responds to food (US), an over-the-counter sensor is the sensible starting point. Stelo and Lingo are very close on price and capability; Stelo offers slightly longer wear and the Dexcom app, while Lingo offers a lower-commitment single-sensor option and Abbott's coaching app. If you specifically have type 2 diabetes and want a sensor built around that, look for Abbott's Libre Rio. The features missing from all of these — real-time alarms, pump integration — are features you do not need.
If you are in Canada, the over-the-counter wellness sensors (Stelo, Lingo) have not launched yet, so the most accessible route is usually the FreeStyle Libre line through a pharmacy — Abbott's Libre has long been available across Canada, sometimes without the prescription friction seen in the US. Check current availability and pricing with your local pharmacy, as this is changing quickly.
Important notes
CGMs are medical devices. Even the consumer-focused products are based on the same underlying sensor technology and produce data that can meaningfully change health decisions. A few things worth keeping in mind:
- Interstitial glucose lags blood glucose by roughly 5 to 15 minutes. When glucose is changing rapidly — during a steep post-meal rise or after exercise — CGM readings trail the actual blood value slightly.
- No CGM is a substitute for medical supervision. If a reading suggests something concerning, confirm with a fingerstick and consult a healthcare provider. The over-the-counter sensors are not intended for anyone on insulin or at risk of low blood sugar.
- Sensor adhesion is the most common complaint across every model. See my CGM adhesion guide for what works for sensors that lift or fall off early.
- Availability and pricing change fast and vary by country. The US over-the-counter market opened only in 2024, Canadian availability differs, and the Accu-Chek SmartGuide is not yet sold in North America at all. Always confirm current local availability and pricing before purchasing.
If you are new to CGMs, my general recommendation is to start with whichever option is most accessible and affordable where you live, and run it for at least one full sensor cycle before judging the experience. Most people find the first two weeks of CGM data dramatically reframes how they think about their own metabolic health, regardless of which device produced it.