How do GLP-1s work?

Key takeaways

• Glucagon-like peptide-1 receptor agonists (GLP-1s) are medications that act like a natural gut hormone. They work by stimulating insulin release, reducing glucagon, and affecting your brain and stomach to decrease appetite and slow digestion.
• GLP-1s may help manage blood sugar in people with type 2 diabetes and support weight loss in people with overweight and obesity. Research suggests people taking GLP-1s for weight management can lose up to 25% of their body weight in 1 year.
• You might notice slight changes in blood sugar soon, but it usually takes about 3 months to see measurable results in A1C levels. For weight loss, subtle changes like reduced appetite may appear early, with continued weight loss for up to a year or longer.

Overview

Glucagon-like peptide-1 receptor agonists (GLP-1s), such as Wegovy, Zepbound, and Ozempic, are medications that are mainly used to manage blood sugar in people with type 2 diabetes and support weight loss in people with overweight and obesity.

GLP-1s get to work in several different ways, including having effects on your brain and your body, and have a wide range of benefits for your health that go beyond weight and blood sugar.

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What are GLP-1s?

GLP-1 is a hormone that’s naturally produced in your gut and released when you eat. It acts as a messenger, targeting receptors in your brain, stomach, and pancreas to signal that the body has received enough fuel from food.

GLP-1 medications contain active ingredients that mimic the natural version of the hormone. Some of these ingredients include:

• semaglutide (Ozempic, Wegovy)
• tirzepatide (Zepbound, Mounjaro)
• dulaglutide (Trulicity)
• orforglipron (Foundayo)

Note that medications containing tirzepatide are dual GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) receptor agonists. GIP is another hormone that works in much the same way as GLP-1.

These medications come as injectable drugs or oral tablets. They’re typically considered to be long-term treatments, and it may be a few weeks or months before you see significant results.

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How do GLP-1s affect blood sugar?

GLP-1s work to reduce blood sugar in people with type 2 diabetes. They affect your blood sugar in two main ways:

• Stimulating insulin secretion: GLP-1s encourage your pancreas to release insulin when your blood sugar levels are raised. Insulin is a natural hormone that helps your body to use sugar as energy, ultimately lowering the level of sugar in your bloodstream.
• Reducing glucagon release: Glucagon is a hormone that raises your blood sugar by triggering your liver to release glucose (a type of sugar). Reducing the release of glucagon can prevent high blood sugar spikes that can occur shortly after eating.

GLP-1s specifically approved for blood sugar management include Ozempic, Mounjaro, and Trulicity.

How do GLP-1s cause weight loss?

GLP-1s can lead to weight loss by having different effects on your appetite. They do this by working on your brain and your stomach.

• Effect on the brain: GLP-1s act on special receptors in your brain to decrease hunger signals and increase feelings of fullness, leading you to eat less. GLP-1s are known for reducing “food noise” — persistent thoughts about food.
• Effect on the stomach: GLP-1s slow down the rate at which your stomach empties, helping you to feel fuller for longer, meaning you feel the need to eat less frequently. This is known as “delayed gastric emptying”.

It’s important to note that GLP-1s are typically prescribed alongside recommendations for increased exercise and changes to your diet to help support your treatment and build healthy habits for the future.

GLP-1s specifically approved for weight management include Wegovy, Zepbound, and Foundayo.

How long do GLP-1s take to work?

GLP-1s get to work in your body right away when you start taking them, but it may be some time before you see results.

You might notice slight reductions in your blood sugar within a week of starting GLP-1s. However, one way doctors monitor your progress is by measuring your A1C levels. A1C tests measure your average blood glucose over an 8- to 12-week period, so it usually takes about 3 months to reflect changes.

For weight loss, you might notice subtle changes early in treatment that aren’t yet reflected by changes on the scale. You might notice you have a slightly reduced appetite or fewer cravings. In the long term, you may continue to see weight loss for up to a year or longer.

According to some 2025 research, people taking GLP-1s for weight management can lose up to 25% of their body weight in one year of treatment.

Learn more about what to expect when you first start taking GLP-1s.

Online care for GLP-1s

If a doctor has prescribed a GLP-1, it’s important to take the medication as directed for as long as your doctor recommends. However, some people might face barriers to accessing these drugs, including high costs and access to healthcare appointments.

Online care may make getting treatment easier. With Optum Perks Online Care, for example, you can get a refill of a weight loss prescription or get help with an existing prescription.

With this service, you can submit an online form answering a few questions about your condition, and a licensed healthcare professional will respond soon after — without the need to make an in-person appointment.

Summary

GLP-1 medications work to reduce your blood sugar and help you lose weight. They do this by mimicking a natural hormone produced in your gut and affecting your brain, stomach, and pancreas to increase insulin levels and reduce appetite and food cravings.

Know that GLP-1s take some time to have a noticeable effect and reach out to your doctor if you have any concerns about how GLP-1s work.

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