Putting on a continuous glucose monitor takes about five minutes and involves three basic phases: preparing your skin, pressing the applicator against your body to insert the sensor, and pairing it with your phone or receiver. The process is designed to be done at home without any medical training, and most modern CGM systems use a spring-loaded applicator that handles the needle insertion automatically.
Choose the Right Placement Site
Where you place the sensor matters for both accuracy and comfort. The Dexcom G7 is approved for the back of the upper arm for anyone age 2 and older, and on the upper buttocks for children ages 2 to 6. The FreeStyle Libre system also uses the back of the upper arm. Pick a spot with enough subcutaneous fat to avoid muscle tissue, and avoid areas that get bumped, compressed, or rubbed by seatbelts, waistbands, or backpack straps.
Rotate your placement site each time you apply a new sensor. Using the same spot repeatedly can cause skin irritation or scar tissue buildup, both of which interfere with accurate glucose readings. Alternating between your left and right arm every sensor session is a simple way to stay on track.
Prepare Your Skin
Good skin prep is the single biggest factor in whether your sensor stays on for its full wear period. Start by washing and thoroughly drying your hands. Then clean the placement site with an alcohol wipe and let it air dry for at least 10 seconds. Don’t blow on it or fan it dry, as that can reintroduce oils or moisture.
The site needs to be free of lotions, sunscreen, and sweat. If you tend to sweat heavily or have had sensors peel off early, applying a thin layer of a liquid adhesive product before insertion can help. Skin Tac is a popular option that’s latex-free and hypoallergenic. A stronger alternative called Mastisol works when other products have failed, though it’s more likely to irritate sensitive skin. If you use a liquid adhesive, leave an empty oval in the center where the sensor filament will go, and let it dry completely before proceeding.
For people who develop skin reactions under the adhesive patch, placing a thin transparent barrier film (like IV3000 or Tegaderm) on the skin first, then inserting the sensor through it, can reduce direct contact between the adhesive and your skin.
Insert the Sensor
Each CGM brand has its own applicator design, but the general process is similar. Here’s what it looks like with the Dexcom G7, one of the most widely used systems:
- Open the applicator. Unscrew or peel off the cap. Don’t touch the inside of the applicator, where the sterile sensor and needle sit.
- Position it on your skin. Press the applicator firmly and flat against the prepared site. You want consistent pressure so the adhesive patch makes full contact.
- Push the button. A spring mechanism drives a small introducer needle just beneath the skin, depositing a tiny flexible filament that stays in place. The needle retracts automatically into the applicator. Most people describe the sensation as a quick pinch or less.
- Secure the adhesive. Rub firmly around the adhesive patch three times in a circular motion, then press gently on the sensor body for about 10 seconds. Warmth and pressure from your fingers help activate the adhesive.
If your system comes with an overpatch (Dexcom includes one in the box), apply it now. Peel the clear liners off one side at a time, center the hole over the sensor, press it down, then remove the colored backing. Rub around the overpatch to seal the edges. A mirror helps if you’re placing it on the back of your arm.
Pair the Sensor With Your Device
Once the sensor is physically in place, you need to link it to your smartphone app or dedicated receiver. For most systems, this means opening the app and following the on-screen prompts to either scan a code on the applicator packaging or enter a sensor code manually. Some systems use a serial number and PIN printed on the applicator cap or packaging label. Keep that packaging until pairing is complete.
Make sure Bluetooth is turned on and your phone is within a few feet of the sensor during the initial pairing. Once connected, the sensor enters a warm-up period before it starts displaying glucose data. This warm-up can be as short as 30 minutes on newer models or as long as 12 hours on older ones. During the warm-up window, you won’t see any readings, so have your fingerstick meter available if you need to check your glucose.
Keep the Sensor Attached for Its Full Wear Period
Most sensors are designed to last 10 to 15 days. The biggest challenge for many people isn’t the insertion but keeping the adhesive intact through showers, exercise, and sleep. A few strategies make a real difference.
Fabric-style adhesive tape like Hypafix provides strong, breathable reinforcement that holds up even when wet. You can cut it to size and frame it around the sensor patch. Transparent film dressings like Tegaderm HP offer thinner coverage with strong holding power, though they’re not breathable and may peel if moisture gets trapped underneath. Experiment to see what works with your skin type and activity level.
If you swim or take long showers, patting the sensor area dry afterward (rather than rubbing) helps preserve the adhesive edges. Some people apply a strip of athletic tape or a pre-cut overlay patch from a third-party supplier for extra security during workouts.
What to Do if Something Goes Wrong
A small amount of bleeding at the insertion site is common and usually harmless. It happens when the introducer needle nicks a tiny capillary. If you see blood pooling under the adhesive patch, apply gentle pressure for a minute or two. In most cases the bleeding stops on its own and the sensor continues to read accurately. If the blood spreads significantly under the patch or the sensor gives erratic readings in the first few hours, replacing it is the safer choice.
If the sensor feels painful after insertion, rather than just the initial pinch, it may have hit a nerve or been placed too close to muscle. You can remove it and try a fresh sensor in a different spot. There’s no need to push through persistent pain.
Remove the Sensor Safely
When the sensor expires, peel the adhesive patch off slowly, pulling it parallel to your skin rather than straight up. If the adhesive is stubbornly bonded, applying an adhesive remover makes a noticeable difference. Dedicated products like Uni-Solve wipes or Tac Away wipes are designed for medical adhesives. A cheaper alternative that works well for most people is baby oil, coconut oil, or olive oil. Let the oil soak around the edges for a minute before peeling.
After removal, clean the site gently with soap and water. Mild redness or a faint outline from the adhesive is normal and typically fades within a day. If you notice a rash, itching, or broken skin, give that area extra time to heal before placing your next sensor nearby.