The Dexcom G7 takes a glucose reading approximately every 5 minutes. That adds up to more than 280 readings per day, giving you a near-continuous picture of your glucose levels without fingersticks.
What Happens Every 5 Minutes
A tiny sensor filament sitting just under your skin measures glucose in your interstitial fluid (the fluid between your cells, not your blood directly). Every 5 minutes, the sensor transmits that reading wirelessly to your smartphone or receiver from up to 33 feet away. The data points are plotted on a graph in real time, so you can see not just your current number but also the direction and speed of any changes.
Because the sensor measures interstitial fluid rather than blood, there’s a slight lag of a few minutes compared to a traditional fingerstick meter. The two numbers won’t always match exactly, and that’s normal. The G7 is factory-calibrated, meaning you don’t need to do any fingerstick calibrations to keep it running. You can optionally enter a fingerstick value if you want to fine-tune it, but the system doesn’t require it.
How This Compares to Other CGMs
The FreeStyle Libre 3 and Libre 3 Plus actually sample more frequently, sending a reading every minute. In practice, though, both systems deliver real-time glucose data to your phone, and the clinical difference between a reading every minute and every 5 minutes is minimal for most daily decision-making. The 5-minute interval on the G7 is more than enough to catch trends, trigger alerts, and build a detailed 24-hour glucose profile.
Warm-Up Period Before Readings Start
When you first apply a new sensor, it doesn’t start giving readings right away. The standard Dexcom G7 has a 30-minute warm-up period, while the newer G7 15 Day version requires 60 minutes. During warm-up, the sensor is calibrating itself to your body’s chemistry. You won’t see any glucose data on your app until this phase is complete, at which point readings begin arriving every 5 minutes.
What Happens When Your Phone Is Out of Range
If you walk away from your phone or your Bluetooth connection drops, the sensor keeps collecting data on its own. Once you’re back in range, the stored readings sync to your app and fill in the gaps on your graph. This backfill feature means a temporary disconnect doesn’t create a permanent hole in your data. That said, you won’t receive any alerts while disconnected, so it’s best to stay within the 33-foot Bluetooth range when possible.
How the G7 Uses Those Frequent Readings
The 5-minute interval isn’t just about showing you a number. The system uses the stream of data points to calculate your glucose trend, displaying an arrow on your screen that tells you whether your levels are rising, falling, or holding steady. It also powers the alert system. You can set custom high and low thresholds, and the G7 will notify you when your glucose crosses them. A predictive alert called “Urgent Low Soon” goes a step further, analyzing your recent readings to warn you up to 20 minutes before your glucose is projected to drop to a dangerously low level.
Over longer periods, those 280-plus daily readings feed into reports like your “time in range” percentage, which shows how much of the day your glucose stayed within your target zone. This metric has become a key tool for tracking glucose management over weeks and months.
Sensor Lifespan and Continuity
The standard G7 sensor lasts up to 10 days before it needs to be replaced. The G7 15 Day version extends that to 15 days. Both versions include a 12-hour grace period after the official wear time ends, giving you a buffer to apply a new sensor without an immediate gap in data. During that grace period, the sensor continues taking readings as usual.
Once you insert a new sensor, you’ll go through the warm-up period again before readings resume. If you’re switching from an expiring sensor to a fresh one, you can start the new sensor session before the old one fully expires to minimize any downtime in your glucose data.