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 or abdomen 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 who were managing insulin dosing in real time. That has changed quickly. Newer consumer-focused CGMs are now available without prescription in many countries and are increasingly 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 | |
|---|---|---|---|
| Manufacturer | Dexcom | Abbott | Dexcom |
| Wear time | 10 days + 12 hour grace period | 14 days | 15 days |
| Warmup | 30 minutes | 60 minutes | 30 minutes |
| Reading frequency | Every 5 minutes | Every minute | Every 15 minutes |
| Calibration required | No | No | No |
| Real-time alerts | Yes (high / low / urgent low) | Yes (high / low) | No real-time alerts |
| Insulin pump integration | Yes | Limited | No |
| Prescription required | Yes (most regions) | Yes (most regions) | No (US) |
| Best suited to | People managing insulin | People managing insulin or doing detailed self-tracking | Wellness users, prediabetes, T2D not on insulin |
The most important thing to understand about this comparison is that these three products are not really competing for the same buyer. They are aimed at three different use cases — and the right choice depends entirely on which one describes you.
The three CGMs in detail
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 in its alert system. It is the only one of the three with a dedicated "urgent low" alarm that will sound even when the phone is silenced, which matters enormously if you are taking insulin. Reported accuracy (MARD, mean absolute relative difference) sits around 8 percent, which is among the best on the market.
The trade-off is access. In most regions the G7 requires a prescription, is priced at the higher end of the CGM market, and is most cost-effective when covered by medical 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 three
- Urgent low alarm overrides silent mode
- Insulin pump integration
- 30-minute warmup
- Reliable real-time data delivery
LIMITATIONS
- Prescription required in most regions
- 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 difference is academic, but for anyone studying their own data closely (looking at 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 lower price point relative to the G7 in most markets. It is the CGM I most often see recommended for people who want clinical-grade data without needing pump integration.
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 in most regions
- 60-minute warmup (longer than G7 and Stelo)
- Alarm system less robust than G7
- Limited insulin pump integration
Stelo
Stelo is Dexcom's response 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 own 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 every five. 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 data stream that 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. It is sold direct-to-consumer in the US without a prescription, typically as a monthly subscription that works out cheaper than the prescription alternatives. For someone whose goal is "I want to understand what foods spike my blood sugar so I can make better decisions," Stelo delivers exactly that, and removes most of the friction.
It is not the right tool for someone managing insulin. It is also not yet available everywhere — at the time of writing it is a US-only product, with international rollout still in early stages.
STRENGTHS
- No prescription required (US)
- 15-day wear (longest of the three)
- Direct-to-consumer subscription model
- Designed specifically for non-insulin wellness use
- Lowest price point
LIMITATIONS
- No real-time low or high alarms
- 15-minute reading frequency
- Not suitable for people on insulin
- Limited international availability
- No insulin pump integration
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 medical insurance coverage. The decision between G7 and Libre 3 typically comes down to whether you use an insulin pump (favouring G7) and which app ecosystem you prefer.
If you have type 2 diabetes managed through lifestyle, prediabetes, or you are simply curious about how your body responds to food, Stelo is the most sensible starting point. It costs less, requires no prescription, and is built for exactly your use case. The features missing from Stelo — real-time alarms, pump integration — are features you do not need.
If you want detailed self-tracking data and live somewhere Stelo is not yet available, FreeStyle Libre 3 with a private prescription is generally the most accessible route. It offers high-resolution data without requiring insulin-pump-grade alarm features.
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 will 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.
- Sensor adhesion is the most common complaint across all three. See my CGM adhesion guide for what works for sensors that fall off early.
- Availability and pricing vary substantially by country. Information in this article reflects general market position; check local availability and current pricing before purchasing.
If you are new to CGMs, my general recommendation is to start with whichever option is most accessible and affordable in your region, 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.