What is GLP-1?
GLP-1 stands for glucagon-like peptide-1 — a hormone naturally produced in your gut in response to food. It plays several roles in regulating blood sugar and appetite: it stimulates insulin release, suppresses glucagon (which raises blood sugar), slows gastric emptying, and signals to your brain that you're full.
GLP-1 receptor agonist medications — commonly called GLP-1 medications — mimic and amplify these effects. By activating GLP-1 receptors more potently and for longer than the body's natural hormone, they produce more powerful effects on blood sugar control, appetite suppression, and weight loss.
The medications were originally developed for Type 2 diabetes management, where their blood sugar lowering effects were the primary goal. The dramatic weight loss observed as a side effect led to their development as dedicated weight loss medications — and to the current wave of widespread use.
How GLP-1 medications produce weight loss
Appetite suppression. GLP-1 receptors in the brain — particularly in the hypothalamus — regulate hunger and satiety. Activating these receptors reduces appetite significantly. Most users report feeling full much faster, losing interest in food between meals, and experiencing less frequent food cravings. This is the primary mechanism behind GLP-1 weight loss.
Slowed gastric emptying. GLP-1 medications slow how quickly food moves from your stomach to your small intestine. This produces a prolonged feeling of fullness after meals and blunts the post-meal glucose spike — the stomach simply releases glucose into the bloodstream more slowly.
Improved insulin sensitivity. Over time, the better glucose control produced by GLP-1 medications reduces the chronic hyperinsulinemia associated with insulin resistance. This improvement in insulin sensitivity has metabolic benefits beyond blood sugar — including improved energy metabolism and reduced fat storage signaling.
Reduced glucagon secretion. GLP-1 medications suppress glucagon release from the pancreas. Since glucagon raises blood sugar by signaling the liver to release stored glucose, suppressing it produces lower overall blood glucose levels — particularly fasting glucose.
Ozempic, Wegovy, Mounjaro — what's the difference?
| Medication | Active ingredient | Approved for | Typical weight loss |
|---|---|---|---|
| Ozempic | Semaglutide | Type 2 diabetes | 10–15% body weight |
| Wegovy | Semaglutide (higher dose) | Weight loss | 15–20% body weight |
| Mounjaro | Tirzepatide (GLP-1 + GIP) | Type 2 diabetes | 15–20% body weight |
| Zepbound | Tirzepatide (higher dose) | Weight loss | 20–25% body weight |
| Victoza/Saxenda | Liraglutide | Diabetes / weight loss | 5–10% body weight |
Ozempic and Wegovy contain the same active ingredient (semaglutide) at different doses. Ozempic is approved for Type 2 diabetes; Wegovy is approved for weight loss. Many people are prescribed Ozempic off-label for weight management when Wegovy is unavailable or cost-prohibitive.
Mounjaro and Zepbound (tirzepatide) are dual GLP-1/GIP receptor agonists — they activate two incretin hormone receptors rather than one. Clinical trials have shown tirzepatide produces greater weight loss than semaglutide on average.
What GLP-1 does to your glucose
Post-meal spikes flatten. The gastric emptying effect of GLP-1 medications directly reduces post-meal glucose peaks. Where a meal might have previously pushed glucose to 170–190 mg/dL, the same meal on GLP-1 medication often produces a peak of 130–150 mg/dL — a meaningful reduction in glucose variability.
Fasting glucose drops. As insulin sensitivity improves and glucagon is suppressed, fasting glucose typically decreases over weeks and months on medication. This is one of the most reliable markers of improving metabolic health on GLP-1s.
Time in range improves. The combination of lower post-meal peaks, reduced fasting glucose, and less glucose variability produces meaningful improvement in time in range — the percentage of time glucose stays in a healthy range. This improvement often precedes and predicts improvements in HbA1c.
CGM makes all of these effects directly visible — which is why GLP-1 users increasingly use continuous glucose monitoring to track their metabolic response to medication.
How CGM helps you optimize GLP-1 treatment
Track medication effectiveness. CGM gives you real-time evidence that your GLP-1 medication is working metabolically — not just on the scale. Seeing your post-meal peaks flatten and your fasting glucose drop is motivating and provides a more complete picture than weight alone.
Optimize diet alongside medication. GLP-1 medications reduce but don't eliminate glucose spikes. CGM shows you which specific foods still cause problematic spikes on medication — allowing you to target dietary changes where they'll have the most additional impact.
Monitor during dose titration. GLP-1 medications are typically titrated slowly — starting at a low dose and increasing over months. CGM shows how each dose change affects your glucose patterns, providing feedback your prescriber sees only via quarterly HbA1c.
Catch low glucose. While GLP-1s rarely cause hypoglycemia on their own, combining them with insulin or sulfonylureas increases risk. CGM provides real-time alerts for low glucose — particularly valuable during sleep.
For most GLP-1 users not on insulin: Dexcom Stelo ($89–99/month, no prescription). For guided metabolic support: Nutrisense (CGM + dietitian coaching). See our full device guide →
Frequently asked questions
Sources & Further Reading
This article draws on the following clinical sources: