How does semaglutide work: Wegovy and Ozempic explained

Key Points

• Semaglutide mimics your body's natural GLP-1 hormone to control blood sugar, reduce appetite, and slow digestion
• Semaglutide is FDA-approved as Ozempic (weekly injectable) and Rybelsus (oral tablet) for type 2 diabetes and Wegovy (weekly injectable) for weight loss
• Clinical studies show 15% average weight loss over 68 weeks with semaglutide
• A nutritious diet and regular exercise are needed for weight loss

With all the buzz around Ozempic and Wegovy, you're probably wondering what's really happening in your body when you take semaglutide.

Clinical studies show people lose an average of 15% of their body weight with semaglutide, but results vary from person to person.

Here's what the research shows about how these medications function and who they're designed to help, with insights from physician Gia Eapen, MD, and Registered Dietitian Rita Faycurry, RD.

What is semaglutide?

Semaglutide is a prescription medication that belongs to a class of drugs called GLP-1 receptor agonists.

It's available under three FDA-approved brand names:

• Ozempic® for type 2 diabetes: a weekly injectable
• Wegovy® for weight loss: a weekly injectable
• Rybelsus® for type 2 diabetes: an oral tablet

More recently, the FDA also approved Wegovy to reduce the risk of severe heart problems in adults who are overweight or obese.

How semaglutide works in your body

"Semaglutide mimics GLP-1, a natural hormone produced in the gut and plays a key role in regulating appetite and blood glucose control," explains Gia Eapen, MD.

Here’s a closer look.

How GLP-1 medications work

In the body, the hormone GLP-1 acts as an efficient messenger, telling your brain when you're getting full so you feel satisfied with less food.

However, this system doesn't work well for everyone. Some people may not produce enough GLP-1, or their brain may not respond strongly to its signals. This can lead to persistent hunger and overeating.

Here's when semaglutide comes to the rescue.

Semaglutide mimics GLP-1 and triggers 4 key actions:

1. Curbs your appetite: Semaglutide tells the appetite center in your brain that you’re full, suppressing your appetite
2. Insulin release: Signals the pancreas to produce insulin for blood sugar control
3. Suppresses glucagon release: Glucagon is a hormone released by the pancreas and raises blood glucose levels. Semaglutide helps suppress this release
4. Slows digestion: Delays stomach emptying so you stay satisfied longer

This powerful mechanism is what makes semaglutide effective for diabetes, weight loss, and heart health.

Who is semaglutide for?

Semaglutide is officially approved for specific groups of people who meet certain criteria:

For weight loss (Wegovy)

Wegovy is approved for use in:

• Adults with a BMI ≥30 (obesity), or
• Adults with a BMI ≥27 (overweight) with at least one weight-related condition:
  • Type 2 diabetes
  • High blood pressure
  • High cholesterol
  • Sleep apnea
  • Cardiovascular disease

For Type 2 diabetes (Ozempic/Rybelsus)

Ozempic and Rybelsus are approved for use in:

• Adults with type 2 diabetes who need better blood sugar control
• Those at high risk for cardiovascular events
• Patients who haven't achieved blood sugar goals with other medications

Wegovy for heart health

Wegovy is approved for use in:

• Adults with established cardiovascular disease who are overweight or obese
• People with type 2 diabetes with heart disease risk factors

You might be a candidate for semaglutide if you:

• Have struggled with traditional diet and exercise alone
• Need to lose weight for health reasons
• Can commit to weekly injections (or daily pills for Rybelsus)
• Are willing to make lifestyle changes alongside medication—diet and exercise are key
• Have realistic expectations about gradual weight loss
• Can afford long-term treatment (insurance coverage varies)

Please consult your healthcare provider about whether semaglutide is right for you.

Off-label considerations

Eapen, MD, says, “While not FDA-approved for these uses, doctors sometimes prescribe semaglutide off-label for PCOS-related weight management, prediabetes prevention, non-alcoholic fatty liver disease (NAFLD), and metabolic syndrome.”

Semaglutide is a prescription medication that should only be used under medical supervision by a healthcare provider.

Who should NOT take semaglutide?

Semaglutide is contraindicated for people with:

• A personal or family history of medullary thyroid carcinoma (MTC)
• Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)
• Type 1 diabetes or diabetic ketoacidosis
• Known allergy to semaglutide or its ingredients
• Currently pregnant or breastfeeding

Discuss with your doctor if you have:

• History of pancreatitis
• History of gallbladder disease
• Severe gastrointestinal problems or gastroparesis
• Diabetic retinopathy
• Severe kidney disease
• History of suicidal thoughts (for weight loss use)

Age restrictions: Semaglutide is not approved for people under the age of 18. However, in specific cases, Wegovy can be used in those aged 12 and above.

Wegovy weight loss results: What to expect

Clinical studies demonstrate weight loss success:

• Average weight loss: 15% weight loss over 68 weeks
• Success rate: Over 86% lose at least 5% of body weight

In comparison, people who made lifestyle changes alone (no semaglutide) lost only 2.4% of their body weight on average.

"While studies have shown that semaglutide is effective for weight loss, please note that individual results may vary. Wegovy is only available through a prescription from a healthcare provider who will evaluate dosage based on your health," says Eapen, MD.

Important: Weight gain is common after stopping semaglutide. The amount of weight gain after you stop taking semaglutide varies from person to person.

Ozempic results for lowering A1C levels: What to expect

"Studies have shown that Ozempic helps reduce A1C in people with type 2 diabetes. It takes weeks to have maximum effect on A1C reduction," says Eapen, MD.

Clinical data shows an average A1C reduction of 2.2% lower A1C with the 2 mg dose and 1.9% with the 1.0 mg weekly dose after 40 weeks (9 months)

How semaglutide protects heart health

The FDA has approved Wegovy (semaglutide) for reducing the risk of serious heart problems in adults who have existing heart disease and are either obese or overweight.

According to the FDA, at the time of approval (March 2025), Wegovy was the first weight loss medication to receive this type of approval.

The clinical evidence

• For people with diabetes: Research indicates that semaglutide can lower the likelihood of major heart events, including strokes and heart attacks, by approximately 20% in overweight or obese individuals without a diabetes diagnosis.
• For people with type 2 diabetes: Another study looking at people with type 2 diabetes, those who received semaglutide were less likely to have a major heart event at any given time compared to patients who got a placebo treatment.

These results were seen when people in the studies took semaglutide injections with lifestyle changes, such as a reduced-calorie diet and regular physical activity.

Semaglutide dosage

Wegovy dosage

Wegovy treatment typically begins with 0.25 mg, the starter dose. This lower starting dose helps your body adjust while minimizing side effects.  After the adjustment period, your healthcare provider may increase your dose gradually.

Wegovy doses are typically increased every 4 weeks.

Wegovy has the following dosage options: 0.25 mg, 0.5 mg, 1.0 mg, 1.7 mg, and 2.4 mg. It's injected under the skin once weekly.

Ozempic dosage

Ozempic (semaglutide for type 2 diabetes) comes in different doses: 0.25 mg, 0.5 mg, 1.0 mg, and 2.0 mg. The medication comes in pre-filled, single-dose pens for injection under the skin, taken once weekly.

Treatment typically begins with 0.25 mg once weekly for 4 weeks. This, again, is to help your body adjust to the drug. After this period, your healthcare provider may increase your dose based on how your body responds to the medication and your health goals.

Semaglutide side effects

"The most frequently reported side effects include nausea, vomiting, diarrhea, constipation, and abdominal pain, notes Eapen, MD. “Your doctor may be able to reduce the intensity of side effects by beginning on a lower dose and then slowly increasing it. Most of these side effects tend to improve as your body adjusts to the medication. If you have persistent side effects, please discuss these with your healthcare provider.”

A small percentage of people report that taking semaglutide leads to feeling tired.

Importance of diet and lifestyle when on semaglutide

Semaglutide works best as part of a complete approach to metabolic health. Even in clinical trials, semaglutide intake for weight loss was combined with lifestyle interventions (diet and exercise).

"I recommend focusing on meals that include lean protein, complex carbohydrates, and healthy fats," explains Faycurry, RD. "Aim for small and frequent meals. Prioritize hydration. Try to avoid  alcohol, sugar, and greasy/fried foods."

A registered weight loss dietitian who specializes in weight management can help you manage your diet on semaglutide. They can provide personalized diet recommendations that work with semaglutide's effects. They allow you to navigate food sensitivities, allergies, and preferences.

Final thoughts: How semaglutide works

Semaglutide is available as Ozempic and Rybelsus for type 2 diabetes and Wegovy for weight management.

Semaglutide mimics a hormone in the body (called GLP-1) that simultaneously targets multiple metabolic pathways. It slows down digestion and tells the pancreas to release insulin. At the same time, it tells the appetite center in the brain that you're full faster, so you end up eating less food.

Remember, semaglutide works best as part of a comprehensive approach including diet, exercise, and medical monitoring. Always consult with healthcare providers to determine if this GLP-1 medication is right for you.

Get a personalized weight loss diet plan, covered by insurance.

Frequently Asked Questions (FAQs)

How does semaglutide help you lose weight?

Semaglutide works for weight loss by mimicking the GLP-1 hormone that naturally controls appetite and digestion. It reduces hunger by targeting brain receptors and slows how quickly food leaves your stomach, so you feel full longer. These combined effects help you naturally eat less and lose weight over time.

How fast can you lose 20 pounds on semaglutide?

Weight loss on semaglutide varies significantly from person to person. Individual factors like starting weight, diet, exercise habits, and metabolism all play important roles. It's worth noting that semaglutide works gradually, and the most sustainable weight loss typically occurs steadily over time rather than rapidly.

Clinical studies provide some helpful context for what you might expect. One study found that people taking semaglutide lost an average of about 15% of their body weight over 68 weeks (approximately 16 months). Another study demonstrated a weight loss of 11 pounds (5kg) over 12 weeks.

How long does it take for semaglutide to start working?

Both weight loss and A1c reductions happen over time with semaglutide. For example, one study demonstrated a weight loss of 5 kg (11 pounds) over 12 weeks.

How do you maximize results on semaglutide?

If you're taking semaglutide, pair it with some healthy lifestyle tweaks. Think of it as a collaborative effort between your medication and daily habits.

Registered Dietitian Rita Faycurry, RD, says, “Focus on eating a balanced diet with plenty of protein, whole grains, and good fats while keeping your calories in check. And try to stay active by mixing cardio with strength training.”

It's important to talk with your healthcare provider about what specific changes are right for you while you're on semaglutide. A registered dietitian can also be incredibly helpful in creating a meal plan that works with your medication and lifestyle.

Start losing weight on semaglutide.

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The views expressed by authors and contributors of such content are not endorsed or approved by Fay and are intended for informational purposes only. The content is reviewed by Fay only to confirm educational value and audience interest. You are encouraged to discuss any questions that you may have about your health with a healthcare provider.