Continuous glucose monitors (CGMs) have made it easier than ever to manage diabetes by providing glucose readings throughout the day and night.
Although inserting a new sensor may seem intimidating the first time, most people quickly become comfortable with the process. Modern CGM systems are designed to make insertion simple, and many patients are surprised by how little discomfort they experience.
This guide explains the general steps for inserting a CGM sensor safely. Because insertion devices differ between manufacturers, always follow the instructions provided with your specific CGM system.
Before You Begin
Gather everything you'll need before opening the sensor package. This typically includes:
- Your CGM sensor and applicator
- Your receiver or smartphone (if needed)
- Alcohol wipes, if recommended
- Adhesive patches or overpatches, if you use them
Wash your hands thoroughly with soap and water before handling your supplies.
Choose the Right Sensor Site
Each CGM manufacturer recommends specific insertion sites based on clinical testing. Common approved locations include the back of the upper arm, the abdomen, and the upper buttocks (for certain devices and age groups). Always use an approved location for your specific CGM model.
Avoid areas that are bruised, scarred, irritated, sunburned, infected, directly under a waistband or tight clothing, or likely to experience repeated friction. Choosing a healthy area of skin helps the sensor function more reliably.
Rotate Your Sensor Sites
Avoid placing every new sensor in exactly the same location. Repeated use of one area may increase skin irritation and reduce adhesive performance. Instead, rotate between approved sites to give your skin time to recover. Many people find it helpful to alternate between the left and right sides of the body.
Prepare Your Skin
Proper skin preparation helps the sensor stay in place. If recommended for your device:
- Wash the area with soap and water.
- Dry the skin completely.
- Clean the site with an alcohol wipe.
- Allow the skin to air dry completely before applying the sensor.
Do not apply a sensor to wet or damp skin — moisture can reduce adhesive strength. Avoid lotions, oils, sunscreen, or creams on the insertion site before application, as these may prevent the adhesive from sticking properly.
Insert the Sensor
Although every CGM system is different, the general process is similar. Typically you will:
- Remove the sensor applicator from its packaging.
- Remove any protective covers according to the manufacturer's instructions.
- Position the applicator firmly against the approved insertion site.
- Activate the applicator.
- Remove the applicator while leaving the sensor attached to your skin.
Most insertion devices automatically place the small sensor just beneath the surface of the skin. The insertion process usually takes only a few seconds.
Does It Hurt?
Most patients describe sensor insertion as causing little discomfort. Some people feel mild pressure, a quick pinch, or brief stinging; others report barely feeling the insertion at all. Discomfort usually resolves within a few minutes.
If you experience severe pain, significant bleeding, or persistent discomfort, remove the sensor if instructed by the manufacturer and contact your healthcare provider or the device manufacturer for guidance.
Start the Sensor
After inserting the sensor, you'll typically need to pair it with your receiver or smartphone, start a new sensor session, and wait through the device's warm-up period.
The warm-up period varies between CGM systems. During this time, glucose readings may not yet be available. Follow your manufacturer's instructions before relying on sensor readings.
Check That the Sensor Is Secure
After insertion, confirm that the adhesive is lying flat against your skin, make sure the sensor feels secure, and avoid pulling or twisting the sensor. If you regularly exercise, swim, or perspire heavily, your healthcare provider may recommend an overpatch or additional adhesive support.
What If the Sensor Bleeds?
A small drop of blood at the insertion site is usually not a cause for concern. Apply gentle pressure with clean gauze or tissue if needed.
However, if you experience persistent bleeding, significant swelling, increasing pain, or signs of infection, contact your healthcare provider.
Common Mistakes to Avoid
Many sensor problems can be prevented with proper technique. Avoid:
- Applying the sensor to irritated skin.
- Using non-approved insertion sites.
- Applying the sensor before the alcohol has dried.
- Touching the adhesive before placement.
- Removing the sensor too soon after insertion.
- Placing the sensor where clothing constantly rubs against it.
Taking a few extra minutes to prepare the site often improves both comfort and sensor performance.
Caring for Your Sensor
Once the sensor is in place, keep the area clean and dry, avoid picking at the adhesive, monitor for redness or irritation, follow the recommended wear time for your device, and replace the sensor when instructed by the manufacturer.
Never continue using a sensor beyond its approved wear period unless specifically directed by your healthcare provider or the manufacturer.
Frequently Asked Questions
Can I shower after inserting my sensor?
Most modern CGM systems are designed to tolerate normal bathing and showering after they have been applied correctly. Follow your manufacturer's instructions regarding water exposure.
Should I shave the insertion site?
Some people with significant body hair find that trimming or shaving the area improves adhesion and makes sensor removal more comfortable. If you shave, avoid irritating the skin before sensor placement.
Is a little redness normal?
Mild redness immediately after insertion may occur and often resolves quickly. Persistent redness, increasing pain, warmth, swelling, or drainage may indicate skin irritation or infection and should be evaluated.
What if the sensor comes loose?
Do not try to tape the sensor back into place if it has become partially dislodged. Depending on the device, you may need to replace the sensor. Follow the manufacturer's instructions and contact customer support if appropriate. See our guide on what to do if your CGM sensor falls off.
When Should You Contact Your Healthcare Provider?
Contact your healthcare provider if you experience significant pain after insertion, the insertion site becomes increasingly red, swollen, or warm, you develop drainage or signs of infection, your sensor repeatedly fails shortly after insertion, or you have questions about proper sensor placement. Many insertion problems can be corrected with small adjustments in technique.
Seek Immediate Medical Care If
Seek urgent medical attention if you develop rapidly spreading redness around the insertion site, severe swelling, fever with signs of skin infection, or difficulty breathing or symptoms of a severe allergic reaction after sensor placement. Although these complications are uncommon, they require prompt medical evaluation.
Tips for Successful Sensor Placement
Patients often find these habits helpful:
- Wash your hands before every insertion.
- Rotate insertion sites.
- Apply the sensor to clean, dry skin.
- Follow your manufacturer's instructions carefully.
- Allow the adhesive to fully attach before vigorous activity.
- Keep extra sensors available in case one needs to be replaced unexpectedly.
With practice, inserting a new sensor becomes a quick and routine part of diabetes management.
The Bottom Line
Inserting a continuous glucose monitor sensor is a simple skill that becomes easier with experience. Choosing a healthy insertion site, preparing your skin properly, following your device's instructions, and rotating sensor locations can help improve comfort, accuracy, and sensor longevity.
If you ever have concerns about sensor placement or skin irritation, your healthcare provider or diabetes care team can help you troubleshoot and ensure you're getting the most from your CGM.