Will my CGM manufacturer replace a failed sensor for free?

Yes — most manufacturers including Dexcom and Abbott will replace sensors that fail within their wear period at no cost. Call their customer support line with your lot number and device serial number. Keep original packaging until the wear period is complete.

How far apart should my new sensor be from my old insertion site?

Place your new sensor at least 3 inches (about 7–8 cm) away from the previous site. Repeated insertions in the same area can cause scar tissue that reduces sensor accuracy and comfort over time.

Can I reuse a transmitter when replacing a failed sensor?

Yes, if your CGM system uses a reusable transmitter (such as the Dexcom G6 or G7 transmitter), you can remove it from the failed sensor and attach it to your new one. Check your transmitter's remaining battery life in your app before reattaching.

Where can I buy replacement CGM sensors quickly?

MDS Diabetes at mdsdiabetes.com carries a wide range of CGM sensors and accessories with home delivery. Ordering a small backup supply ensures you always have a replacement ready if a sensor fails unexpectedly.

Replacing a Failed CGM Sensor: Step-by-Step Guide

Key takeaways

✓Always verify a failed sensor with a fingerstick before changing insulin doses or inserting a replacement
✓Rotating your insertion site and storing sensors properly significantly reduces failure rates
✓Keeping backup sensors on hand — available at mdsdiabetes.com — prevents dangerous monitoring gaps

What Is a CGM Sensor Failure?

Continuous glucose monitors (CGMs) have transformed diabetes management, but even the best sensors can fail before their intended wear period ends. A sensor failure occurs when your device stops delivering accurate, reliable glucose readings — whether due to a compression error, insertion problem, signal loss, or manufacturing defect. Knowing how to respond quickly and correctly can minimize gaps in your glucose monitoring and keep you safe.

Recognizing the Signs of a Failed Sensor

Before you replace a sensor, confirm it has actually failed. Common failure indicators include:

Persistent "Signal Loss" or "No Readings" alerts lasting more than 30 minutes
Readings that are wildly inaccurate compared to fingerstick blood glucose checks
"Sensor Error" or "Failed Sensor" messages on your receiver or smartphone app
Physical issues such as a dislodged sensor, visible bleeding under the patch, or a bent cannula
Consistent arrows showing extreme rises or falls that don't match how you feel

Always verify a suspicious reading with a fingerstick before taking action on insulin dosing. Never rely on a sensor you suspect has failed.

Step-by-Step: Replacing Your Failed CGM Sensor

Step 1 — Remove the Failed Sensor

Peel back the adhesive patch gently from one edge, pressing down on the skin as you go to reduce discomfort. Remove the transmitter first if your system uses a reusable transmitter (such as Dexcom G6 or G7). Dispose of the used sensor in a sharps container or manufacturer-provided disposal bag.

Step 2 — Choose a New Insertion Site

Rotate your site to avoid scar tissue buildup, which reduces sensor accuracy over time. Recommended sites vary by system — common options include the abdomen, upper arm, or upper buttocks. Avoid areas with waistbands, seatbelts, or frequent bending. Leave at least 3 inches between your new site and the previous one.

Step 3 — Prepare Your Skin

Clean the new site with an alcohol swab and allow it to dry completely — at least 30 seconds. Damp skin can weaken adhesive and affect filament insertion. If you use a skin barrier wipe or adhesive prep pad, apply it now and let it dry before inserting.

Step 4 — Insert the New Sensor

Follow your specific CGM system's insertion instructions carefully. For most auto-inserters, press firmly and flat against the skin, then trigger the inserter and remove it smoothly. Apply gentle pressure around the adhesive to secure it. Attach your transmitter if required.

Step 5 — Complete the Warm-Up Period

All CGM sensors require a warm-up period — typically 30 minutes to 2 hours depending on your system. During this window, continue fingerstick monitoring. Do not skip calibration steps if your device requires them.

Step 6 — Confirm Accuracy

Once readings resume, compare the first CGM reading against a fingerstick. If the values are within 20%, your sensor is working correctly. If not, allow another 30 minutes and recheck before considering a second replacement.

When to Request a Sensor Replacement from the Manufacturer

Most CGM manufacturers — including Dexcom and Abbott — will replace sensors that fail within their warranted wear period at no charge. Contact their support line with your sensor lot number and the exact error message. Keep your packaging until the wear period ends for this reason.

Keeping Replacement Sensors on Hand

Running out of sensors during a failure is a stressful and dangerous situation. Maintaining a small backup supply ensures you're never left without coverage. MDS Diabetes offers a reliable selection of CGM sensors, transmitters, and accessories, making it easy to stock up and stay protected. Ordering through mdsdiabetes.com means you get competitive pricing with the convenience of home delivery — ideal for building a consistent supply routine.

Tips to Prevent Future Sensor Failures

Store sensors at room temperature and away from direct sunlight
Check expiration dates before inserting any sensor
Avoid inserting over scar tissue, tattoos, or areas with poor circulation
Use extra adhesive overlays in humid climates or if you sweat heavily during exercise
Handle sensors by the edges and avoid touching the filament tip

References & Sources

Frequently asked questions

Wait at least 30 minutes after a signal loss or error before replacing. Compare any available readings to a fingerstick. If errors persist beyond 30–60 minutes or readings are consistently more than 20% off from fingersticks, the sensor has likely failed and should be replaced.

Editorial note

This article is for educational purposes only and does not constitute medical advice. Always consult your healthcare provider before making changes to your diabetes management. Last reviewed: July 12, 2026 by the MDS Diabetes editorial team.

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