How GLP-1 medications affect blood sugar
GLP-1 medications like semaglutide and tirzepatide lower glucose through several mechanisms at once: here's what's happening and what to watch.
In short: GLP-1s lower glucose mainly by boosting insulin when it's needed, slowing digestion, and reducing appetite.
GLP-1 receptor agonists, semaglutide (Ozempic, Wegovy) and the dual GIP/GLP-1 agonist tirzepatide (Mounjaro, Zepbound), mimic a gut hormone your body releases after eating. They prompt the pancreas to release insulin only when glucose is elevated, which is why they rarely cause lows on their own, and they lower the glucagon signal that tells the liver to release more glucose.
They also slow how quickly the stomach empties, so the carbohydrates in a meal arrive more gradually and the after-meal spike is gentler. Combined with reduced appetite, many people see both their average glucose and their weight drift down over the first weeks and months.
Because the effect builds as the dose is increased, the clearest way to see it working is to track consistently: a steady or rising time in range, a falling average, and weight coming down together, read over weeks rather than any single reading.