The Dexcom G6 is FDA-cleared for the abdomen in adults and the abdomen or upper buttocks in children ages 2 to 17. The back of the upper arm is not an FDA-approved site, and clinical data shows sensors placed on the arm have a statistically worse accuracy compared to the abdomen. That said, many people with diabetes do use the arm in practice, and the insertion process itself is the same regardless of location. Here’s what you need to know if you choose this site.
Why the Arm Isn’t Officially Approved
Dexcom’s FDA clearance specifically states that sensor performance has not been evaluated at sites other than the abdomen and upper buttocks, and readings “may differ from expected iCGM performance.” Research presented through the American Diabetes Association found that sensors placed on the arm had a worse Mean Absolute Relative Difference (a measure of how far sensor readings stray from actual blood glucose) compared to sensors on the abdomen. In plain terms, arm readings may be less reliable, especially during exercise or rapid blood sugar changes.
Despite this, many users prefer the arm because it’s less visible under clothing, more comfortable for sleep, and easier to forget about during the day. If you decide to use the arm, be aware that you may need to verify readings with a fingerstick more often than you would with an abdominal placement.
Choosing the Right Spot on Your Arm
The back of the upper arm, roughly halfway between your shoulder and elbow, is the area most commonly used. You want a spot with a small layer of fat rather than pure muscle. Pinch the back of your arm: if you can grab a fold of tissue, that’s a workable location. Avoid areas directly over bone, near your elbow, or on the outer side of your arm where clothing tends to rub.
Pick a spot you can reach comfortably, because you’ll be pressing the applicator firmly against your skin. If you have limited flexibility, the arm can be tricky to do solo, and many people ask a partner or family member to help with insertion.
Step-by-Step Insertion
Start by washing the area with soap and water, then let it dry completely. Don’t apply lotion, sunscreen, or any moisturizer to the spot beforehand. Oils on the skin weaken the adhesive and can cause the sensor to peel early.
Peel open the sensor applicator packaging and remove the safety cap by twisting it off. You’ll see the adhesive pad with the applicator barrel in the center. Hold the applicator like you’re gripping a large marker, with your thumb and fingers around the barrel. Press the adhesive pad flat against the back of your upper arm. You need firm, even contact with the skin before you push the button.
Once the adhesive is fully stuck down, press the orange button on top of the applicator. You’ll hear a click, and the sensor wire will insert under the skin automatically. The sensation is quick, similar to a brief pinch. Pull the applicator straight away from your arm. The sensor and its adhesive pad stay behind.
Next, snap the transmitter into the sensor housing. It clicks into place. Open your Dexcom app or receiver and follow the pairing prompts. The G6 requires a two-hour warmup period before it begins displaying readings.
Keeping the Sensor Secure for 10 Days
Arms take more abuse than abdomens. Sleeves, seatbelts, bag straps, and doorframes can all catch the edge of a sensor and peel it up. Securing the adhesive from day one saves a lot of frustration later in the session.
The simplest option is an overpatch. Cut a hole in the center of a medical adhesive patch so it fits around the transmitter, then press the patch down over the sensor’s existing adhesive. This “picture frame” technique reinforces the edges without covering the transmitter itself. Dexcom offers free overpatches through their website, or you can use products like Hypafix (a thick, fabric-like adhesive that holds well even when wet), Tegaderm HP (a thin transparent film with strong holding power), or IV3000 (another transparent film that tends to cause fewer skin reactions than Tegaderm).
For even stronger hold, apply a liquid skin adhesive before insertion. Products like Skin Tac or Mastisol create a tacky layer that bonds the sensor pad more firmly to your skin. The technique is to paint an oval of the liquid adhesive on your arm, leave the center clean, let it dry until tacky, and then insert the sensor on the clean skin in the middle. The adhesive pad’s edges land on the tacky oval. Skin Tac is latex-free and hypoallergenic, making it a good starting point. Mastisol is stronger but more likely to irritate sensitive skin.
If you tend to sweat heavily, fabric-based adhesives like Hypafix outperform transparent films, which can trap moisture underneath and start to peel.
Rotating Your Arm Sites
Using the same exact spot every 10 days can cause skin irritation, scar tissue buildup, and worse sensor performance over time. Move your insertion point a few inches each session using a simple grid pattern. Think of the back of your upper arm as a small box divided into four quadrants. Use one quadrant per session, cycling through all four before switching to the other arm.
Finish all four positions on one arm before moving to the other side. This gives each spot roughly 40 days of rest between uses. If you also wear an insulin pump site on your arm, keep the sensor and pump at least three inches apart to avoid interference.
Common Issues With Arm Placement
Compression lows are the most frequent complaint. If you sleep on the arm with the sensor, your body weight presses on the sensor wire and causes falsely low readings, sometimes triggering alarms in the middle of the night. The readings return to normal once pressure is removed. Sleeping on your back or opposite side is the simplest fix.
Sensor adhesive lifting at the edges is more common on the arm than the abdomen because of constant arm movement. If you notice a corner peeling up in the first few days, reinforcing it with a strip of medical tape immediately can save the session. Once the adhesive edge folds over on itself, it won’t re-stick.
Some people notice their readings on the arm lag slightly behind fingerstick values, particularly after meals or during exercise. All CGM readings trail actual blood glucose by about 5 to 15 minutes because the sensor measures glucose in the fluid between cells, not in the blood directly. This lag can be slightly more pronounced on the arm. If you’re making insulin dosing decisions during rapidly changing blood sugar, a confirmatory fingerstick is a reasonable habit.