The Dexcom G7 sensor lasts up to 10 days, plus a 12-hour grace period at the end. That gives you a maximum of 10.5 days of glucose readings from a single sensor before you need to apply a new one. Dexcom also offers a newer G7 15 Day version, which extends wear time to 15 days with the same 12-hour grace period.
How the 10-Day Session Works
Once you insert the G7 sensor and it completes its warm-up, a 10-day countdown begins. During this window, the sensor continuously measures your glucose and sends readings to your phone or receiver. When those 10 days are up, the system doesn’t cut off immediately. Instead, you enter a 12-hour grace period where the sensor keeps functioning normally, giving you time to apply a new one without a gap in data.
After the grace period ends, readings stop entirely. You cannot restart or extend the session. Dexcom has designed the G7 so that restarting a used sensor is not possible, unlike workarounds some users found with older models. You’ll need to open a fresh sensor and start a new session.
Real-World Wear Time Is Often Shorter
While 10 days is the labeled duration, many people don’t get the full session. A study of youth and young adults with type 1 diabetes found the median wear time was 8.6 days. About a quarter of sensors were removed before day 7, and only 40% made it to day 10 or beyond. Early removal happens for a range of reasons: adhesive peeling off, sensor errors, skin irritation, or simply getting knocked loose during activity.
Accuracy Across the 10 Days
Sensor accuracy isn’t perfectly uniform from start to finish, but it stays reliable throughout the full wear period. In clinical testing, readings from arm-placed sensors were least accurate on day 1 (about 11.9% off from a lab blood glucose measurement) as the sensor settled in. By day 4, accuracy improved significantly and held steady through day 10 and even into the grace period. Sensors placed on the abdomen followed the same pattern, with slightly less precision overall.
In practical terms, this means your first day of readings may be a bit less dependable than the rest of the session. If you notice readings that seem off in those initial hours, that’s a known pattern and not necessarily a sign of a faulty sensor.
Common Reasons Sensors Fail Early
The G7 monitors its own performance, and if it detects it can no longer get a reliable glucose reading, it will alert you. There are two stages to this. First, you may see a “Brief Sensor Issue” alert, meaning the sensor is temporarily unable to measure glucose. This is most common on the first day and usually resolves within three hours. If the problem doesn’t resolve, you’ll get a “Sensor Failed” alert, which means the session is over and you need to remove the sensor and start a new one.
Several factors increase the chance of early failure:
- Poor placement. Inserting over areas with loose skin, not enough fat, or near bones and muscles can interfere with the sensor wire’s ability to read glucose in your interstitial fluid.
- Physical contact. Placing the sensor where it gets bumped, compressed during sleep, or rubbed by a waistband leads to signal issues and adhesive failure.
- Proximity to insulin sites. Inserting within 3 inches of an infusion set or injection site can distort readings.
- Skin preparation. Inserting on skin that wasn’t clean or fully dry compromises the adhesive bond from the start.
Keeping the Sensor Attached for the Full Session
Adhesive failure is one of the most common reasons people lose a sensor early. The G7’s built-in adhesive patch works well for many users, but if you’re active, sweat heavily, or swim regularly, you may need extra help. Dexcom recommends using an overlay patch (included with each sensor) and keeping the sensor securely pressed to your skin so the tiny sensor wire stays in place.
For additional hold, liquid adhesive products can be applied to the skin before insertion. Skin Tac is a popular option with strong adhesive properties and a latex-free formula. Mastisol is even stronger and works when other products haven’t held, though it’s more likely to irritate sensitive skin. When using any liquid adhesive, apply it in a ring around where the sensor will sit, leave the center clean, let it dry, then insert the sensor on the bare skin in the middle.
Adhesive patches or medical tapes placed over the sensor offer another layer of security. Hypafix is a fabric-like tape that holds well even when wet and tends to be gentler on skin at removal. Transparent films like Tegaderm HP or IV3000 are thinner and less noticeable but can peel if moisture gets underneath. You can cut a hole in the center of any of these to fit around the transmitter, or use strips in a “picture frame” pattern around the edges of the sensor’s adhesive pad.
What to Do if a Sensor Fails Early
If your G7 sensor stops working before the 10-day session is complete, Dexcom will replace it at no cost if the failure is confirmed as a product issue. Contact their tech support as soon as possible after the failure. They’ll review the case, and if the sensor didn’t meet its published performance expectations, a replacement ships with no limit on how many times you can request one. Even if the failure turns out to be non-product related (like an application error or early removal for a medical procedure), you may still receive a courtesy replacement.
G7 15 Day: The Extended Option
Dexcom’s G7 15 Day sensor uses the same physical design but runs a different algorithm that allows five additional days of wear. It requires a 60-minute warm-up period before readings begin. After the 15-day session, the same 12-hour grace period applies, giving you a maximum of 15.5 days from a single sensor. For people who want fewer sensor changes per month, this cuts the number of insertions roughly in half compared to the standard G7, going from about three sensors per month to two.