Dexcom G8 Review 2026: 30-Day Sensor, Ketone Monitoring, 40% Smaller

Diabetes Technology · 5 · February 23, 2026

The Dexcom G7 was good. The G8 is a different category. Approved January 2026, it addresses the three biggest complaints about every CGM on the market: the sensor is too bulky, it needs replacing too often, and it only tracks glucose.

What Changed

30-day sensor life. The G7 lasted 10 days. The Libre 3 lasts 14. The G8 lasts 30. That means one sensor insertion per month instead of three. Less medical waste. Less skin irritation. Less cost if you are paying out of pocket — roughly $89 per month instead of $270 for three G7 sensors.

40% smaller form factor. The G8 sensor is barely noticeable under a shirt sleeve. Dexcom achieved this by integrating the transmitter directly into the sensor pod — no separate transmitter to snap on. One piece. Thinner. Lighter.

Ketone monitoring. This is the feature that matters most for Type 1 patients and anyone on a ketogenic diet. The G8 continuously measures beta-hydroxybutyrate (BHB) alongside glucose. Ketone levels above 3.0 mmol/L can indicate diabetic ketoacidosis — a medical emergency. Having this detected automatically, continuously, without a separate fingerstick ketone meter, could save lives.

How It Connects

Bluetooth 5.0 to your phone. Compatible with Dexcom's app and — because it uses the standard Glucose Service UUID — with third-party platforms like Journey for Health's CGM Monitor. The platform adds Glucose Weather, crash prediction, and ARIMA-based 2-hour forecasting on top of the raw Dexcom data. Features Dexcom's own app does not offer.

Still Not Needleless

The G8 still uses a subcutaneous filament. The insertion needle is 40% thinner than the G7 — most users report zero pain — but it is still technically invasive. For truly needleless options, Samsung's glucose-sensing contact lens and Know Labs' Bio-RFID wristband are in clinical trials but 2–3 years from market. Track their progress at Diabetes Breakthroughs.

For now, the G8 is the closest thing to "wear it and forget it" glucose monitoring. One sensor per month. Ketone alerts. Invisible under clothing. If your insurance covers Dexcom, ask about the G8 upgrade.