A CGM patch is a wearable sensor that reads glucose in the fluid under your skin and sends the numbers to your phone every few minutes.
A small sensor sits just beneath the skin and measures glucose in interstitial fluid, not blood. Readings travel wirelessly to an app or receiver showing your current glucose, trend, and — depending on the system — alerts for highs and lows. “Patch” usually means the adhesive wearable part; a full system can also include a transmitter, applicator, software, and optional receiver. The FDA cleared the first over-the-counter version for US adults in May 2024.
Two details matter: CGM readings come from interstitial fluid, so they can differ from a finger-stick meter, especially when glucose changes fast. And not every “glucose patch” is a real medical device.
How Does a CGM Patch Actually Work?
A CGM patch inserts a thin sensor into interstitial fluid, measuring glucose continuously and transmitting data to a paired display. Most adhesive systems follow the same sequence; exact sites, warm-up times, and pairing vary by model.
- Pick an approved site named in your product’s instructions.
- Clean and dry the skin so the adhesive holds for the full wear period.
- Apply the sensor with the manufacturer’s applicator — nothing is inserted by hand.
- Pair it with the official app or receiver and wait through startup before trusting any number.
- Replace the sensor at the stated wear limit and respond to alerts as directed.
One system breaks the pattern. Eversense E3 uses a clinician-implanted sensor plus an external transmitter held with adhesive. Insertion and removal require a qualified healthcare professional, and it needs fingerstick calibration: twice daily for the first 21 days, then once daily unless your clinician says otherwise.
Interstitial fluid lags behind blood glucose, so a CGM can read low while you’re fine — or the reverse. Some systems still require confirmatory fingersticks in specific situations, including symptoms that don’t match the screen.
Which CGM Patch Systems Are Available in the US?
Five FDA-cleared or approved systems cover most US buyers, differing in who they’re for, sensor lifespan, and cost.
| System | Who It’s For | Wear Time and Update Rate | Typical Out-of-Pocket Cost |
|---|---|---|---|
| Dexcom Stelo | Adults 18+ who don’t use insulin, including those on oral medication and people without diabetes | Up to 15 days per sensor; updates every 15 minutes | Over-the-counter; no prescription needed |
| Dexcom G7 | People with diabetes aged 2 and older | Readings without routine fingersticks; pairs with Tandem t:slim X2, Tandem Mobi, and Omnipod 5 | $0 for most covered patients |
| Dexcom G7 15 Day | Same population as G7 | Extended 15-day sensor version | $0 for most covered patients |
| Abbott FreeStyle Libre 3 | People with diabetes using a compatible smartphone | Wearable sensor with app-based glucose views | $80 or more per month for most covered patients |
| Abbott FreeStyle Libre 3 Plus | Children aged 2 and older with diabetes | Wearable sensor with app-based glucose views | $80 or more per month for most covered patients |
| Eversense E3 | Adults 18+ with diabetes | Implanted sensor worn up to 180 days; readings every 5 minutes; fingerstick calibration required | Professional insertion required |
Stelo is the only over-the-counter option and isn’t intended for people with problematic hypoglycemia because it doesn’t alert for that condition.
If you’re weighing which model fits your budget and routine, this roundup of the best CGM patches we tested walks through the trade-offs buyers hit most often.
What a CGM Patch Cannot Do
A CGM patch cannot measure glucose through your skin without piercing it, or replace every fingerstick for every user. The FDA warns that smartwatches and smart rings claiming non-piercing glucose measurement are not authorized, cleared, or approved.
- Labeled populations exist for a reason. Using Stelo while taking insulin, or relying on it for problematic hypoglycemia, falls outside its cleared use.
- Alerts aren’t universal. Not every system offers high- and low-glucose alerts, and some are built for people who don’t need them.
- App support varies. Some systems pair with compatible insulin-delivery devices; others are display-only.
A real CGM patch is a regulated device with a documented wear limit and labeled population; anything marketed as a skin-deep glucose reader without that paperwork isn’t one.
Common Questions
Does a CGM patch hurt to apply?
Most users describe a brief pinch; insertion takes seconds. The larger annoyance is often the adhesive, especially late in a wear cycle. If a site stays irritated or the patch won’t hold, move to a different approved spot and follow your product’s instructions.
Can you shower or swim while wearing one?
Adhesive CGM sensors are designed to stay on through normal daily activity, including showering, in most cases. Water tolerance and depth limits are set by the manufacturer, so check your model’s instructions before swimming. Eversense’s transmitter is held with adhesive, so the same product-specific guidance applies.
Why is my reading different from a finger stick?
A CGM measures glucose in interstitial fluid, which trails blood glucose when levels change fast; a gap of a few minutes is expected. When symptoms don’t match the display, follow your system’s instructions — some require a confirmatory fingerstick in exactly that situation.
Sources
- U.S. Food and Drug Administration. “FDA Clears First Over-the-Counter Continuous Glucose Monitor.” Confirms Stelo’s May 3, 2024 clearance, the 18+ population, and the 15-day sensor with 15-minute updates.
- U.S. Food and Drug Administration. “Continuous Glucose Monitoring Systems — Device Classification and Labeling Documentation.”
- U.S. Food and Drug Administration. “Do Not Use Smartwatches or Smart Rings to Measure Blood Glucose Levels.” States that non-piercing smartwatch and smart ring glucose claims are not FDA-authorized.