Encyclopedia entry

Continuous Glucose Monitor (CGM)

A continuous glucose monitor is a wearable sensor (typically a small coin-sized adhesive patch) that reports interstitial glucose levels every 1 to 5 minutes for 10 to 14 days. Originally developed for type 1 and insulin-dependent type 2 diabetes management; increasingly used in longevity and metabolic health monitoring by people without diabetes.

UK availability

• · FreeStyle Libre 2 / Libre 3 (Abbott): the most widely used UK CGM. NHS-prescribed for eligible diabetes patients. Privately available at approximately £50 to £100 per 14-day sensor.
• · Dexcom G7: alternative, mostly NHS-prescribed for type 1 diabetes. Privately available.
• · Zoe, Veri, Levels: consumer-facing wellness brands that wrap a CGM (typically Libre) in a coaching app. Subscription model.

What a CGM tells you

• · Glucose level moment by moment.
• · Time-in-range (typically 70 to 180 mg/dL for non-diabetics aiming wider; 70 to 140 for tighter control).
• · Glucose variability: how much your glucose moves through the day.
• · Postprandial spikes: glucose response to specific meals.
• · Overnight glucose, exercise glucose, stress glucose.

What a GLP-1 user sees on CGM

Patients on GLP-1 medications typically see flattened postprandial curves, lower glucose variability, and reduced fasting glucose. This is the underlying mechanism by which GLP-1 was first developed for type 2 diabetes management; the weight-management benefit followed. For non-diabetic users on GLP-1, CGM can show how the medication is changing glucose handling beyond what the scale weight reveals.

Caveats for non-diabetic use

Most "ideal" CGM ranges and the postprandial-spike interpretation framework come from diabetes literature. Healthy non-diabetic glucose variability is wider than wellness apps sometimes imply. Brief postprandial spikes after carbohydrate-rich meals are physiologically normal, not necessarily a problem. CGM in healthy adults is informational, not diagnostic.

Related: HbA1c · GLP-1 mechanism.