Changing a Dexcom G7 sensor takes about five minutes and follows a simple sequence: remove the old sensor, clean your skin, insert the new one with the auto-applicator, and pair it through your app. The G7 lasts up to 10 days, with a 12-hour grace period after the session expires where you’ll still get readings. Once that grace period ends, the sensor stops working and needs to be replaced.
When to Change Your Sensor
Your Dexcom app will notify you as the 10-day session winds down. After the session officially ends, you have 12 hours of grace period where the sensor continues reading your glucose. You can swap the sensor at any point during that window, or wait until readings stop entirely. Many people find it easiest to change the sensor in the morning so the warmup period finishes before the busiest part of their day.
The newer G7 15 Day sensor, available for adults 18 and older, extends wear to 15 days but requires a longer 60-minute warmup compared to the standard G7’s 30-minute warmup.
Removing the Old Sensor
Start by loosening one edge of the adhesive patch with your fingernail. As you peel, use your opposite hand to press the skin down and away from the adhesive. This reduces tugging and makes removal more comfortable. Peel slowly at a low angle, folding the patch back on itself rather than pulling it straight up.
Adhesive residue is common. You can dissolve it with baby oil, coconut oil, or olive oil, which is the cheapest and simplest option. Dedicated adhesive remover wipes from brands like Uni-Solve or Tac Away also work well if you prefer something purpose-built. Gently rub the product under the remaining adhesive until the residue lifts off.
Dexcom recommends disposing of used applicators and sensors following your local guidelines for blood-containing components. Some areas require a sharps container; others allow household trash. Check what your municipality requires.
Preparing Your Skin
Wash the new insertion site with oil-free, antimicrobial soap and dry it thoroughly. Any oil, lotion, or moisture left on the skin will weaken the adhesive bond and may cause the sensor to peel off before the full 10 days.
If you tend to sweat heavily, apply unscented solid or spray antiperspirant in an oval shape over the area and wait 10 to 15 minutes before inserting. Place the sensor in the center of that oval so the antiperspirant sits underneath the adhesive edges.
For sensitive skin that reacts to the adhesive, a barrier layer between your skin and the patch can help. You have two main options. Barrier films like Cavilon No Sting Barrier or SurePrep are painted directly onto the skin in an oval, then allowed to dry completely before insertion. Alternatively, thin hydrocolloid dressings or transparent films (like IV3000 or Opsite Flexifix) can be placed on the skin first, with the sensor inserted through the dressing. Some people also spray two puffs of over-the-counter fluticasone nasal spray (the active ingredient in Flonase) onto the site and let it dry for two minutes before inserting. This can reduce skin irritation from the adhesive.
Choosing an Insertion Site
For adults, the only approved location is the back of the upper arm. For children ages 2 and older, the back of the upper arm is also approved, with the upper buttocks as an additional option for children ages 2 through 6.
Rotate between your left and right arm with each sensor change. Avoid placing the new sensor directly on top of where the old one sat. Giving the skin a break between sessions helps prevent irritation buildup and keeps adhesion strong.
Inserting the New Sensor
Pick up the new applicator and unscrew the cap. Don’t touch the inside of the applicator, where the sensor and needle are housed. Place the open end of the applicator flat against your skin, pressing firmly so there’s good contact. Then push the button on top. You’ll hear a click as the sensor deploys under your skin. The applicator automatically retracts the insertion needle, leaving only the tiny sensor filament in place.
Don’t use excessive downward pressure when you push the button. Pressing too hard can drive the sensor deeper than intended, which increases the chance of hitting a small blood vessel. If you notice bleeding at the insertion site, it doesn’t necessarily mean the sensor has failed. Contact Dexcom’s technical support line (available 24/7) to check whether the sensor needs replacing or if it’s fine to continue wearing.
Pairing With Your App
After insertion, open the Dexcom G7 app on your phone. You’ll need the 4-digit pairing code printed on the applicator you just used, so don’t throw it away yet. You can either take a photo of the code with your phone’s camera or type it in manually.
Keep your phone within 20 feet of the sensor during pairing and the entire warmup period. The standard G7 warms up in about 30 minutes, after which glucose readings will begin appearing automatically. If you’re using the G7 15 Day sensor, expect a 60-minute warmup before your first reading.
Keeping the Sensor On for 10 Days
The adhesive patch holds well for most people, but edges can start peeling after several days of showers, exercise, or humid weather. Dexcom provides overpatches specifically designed for the G7’s shape.
Timing the overpatch depends on your skin type. If your skin tends to be oily or you sweat a lot, apply the overpatch right after inserting the sensor. If your skin is drier or less elastic, wait and see whether the edges actually start lifting before adding one. You can also use medical tape as an alternative to the official overpatch.
The overpatch goes over the top of the existing sensor adhesive, not directly on your skin underneath the sensor. It reinforces the edges that are most likely to curl up over time.