SemaglutideAlso known as: Ozempic / Wegovy / Rybelsus

Mechanism of Action

Semaglutide is a GLP-1 receptor agonist—it mimics the effects of glucagon-like peptide-1, an incretin hormone naturally released by the gut after eating.

Appetite Suppression

GLP-1 receptors in the hypothalamus regulate satiety and food intake. Semaglutide activates these receptors, reducing hunger and increasing feelings of fullness. Most users describe a fundamental shift in their relationship with food—cravings diminish, and smaller portions become satisfying.

Delayed Gastric Emptying

Semaglutide slows the rate at which food leaves the stomach, prolonging the feeling of fullness after meals. This contributes to reduced caloric intake but can also cause GI side effects (nausea, bloating) until adaptation occurs.

Glycemic Effects

• Enhanced insulin secretion: Glucose-dependent (low hypoglycemia risk)
• Suppressed glucagon: Reduces hepatic glucose production
• Improved insulin sensitivity: Particularly with weight loss

Clinical Evidence

STEP Trials (Obesity)

The STEP program established semaglutide as a breakthrough obesity treatment:

• STEP 1: 16.9% weight loss at 2.4mg over 68 weeks (vs 2.4% placebo)
• STEP 2: 9.6% weight loss in patients with diabetes
• STEP 3: 16% weight loss with intensive behavioral therapy
• STEP 4: Continued treatment maintained weight loss; discontinuation led to regain

SELECT Trial (Cardiovascular)

The SELECT trial demonstrated cardiovascular benefits in patients with obesity without diabetes:

• 20% reduction in major cardiovascular events (heart attack, stroke, CV death)
• Benefits observed independent of weight loss magnitude
• First GLP-1 to show CV benefit in obesity without diabetes

Dosing Protocols

Wegovy (Weight Management) Titration

• Weeks 1-4: 0.25mg weekly
• Weeks 5-8: 0.5mg weekly
• Weeks 9-12: 1.0mg weekly
• Weeks 13-16: 1.7mg weekly
• Week 17+: 2.4mg weekly (maintenance)

Ozempic (Diabetes) Dosing

• Starting: 0.25mg weekly for 4 weeks
• Then: 0.5mg weekly
• Maximum: 2.0mg weekly if needed for glycemic control

Side Effects

Gastrointestinal (Very Common)

• Nausea: 40-50% (usually improves by week 8-12)
• Diarrhea: 30%
• Vomiting: 20-25%
• Constipation: 20-25%
• Abdominal pain: 15-20%

Management: Eat smaller meals, avoid fatty foods, stay hydrated, use slower titration if needed. GI side effects typically diminish with continued use.

Semaglutide vs Tirzepatide

For a detailed comparison, see our Tirzepatide profile. Key differences:

• Weight loss: Tirzepatide ~22% vs Semaglutide ~17%
• Mechanism: Tirzepatide is dual GLP-1/GIP; Semaglutide is GLP-1 only
• Experience: Semaglutide has longer track record and more data
• Cost/availability: Both are expensive; availability varies

Frequently Asked Questions

How much weight can you lose on semaglutide?

Clinical trials showed average weight loss of 15-17% of body weight at 2.4mg weekly over 68 weeks. Individual results range from 10-20%+ depending on adherence, diet, and exercise.

What is the difference between Ozempic and Wegovy?

Both contain semaglutide. Ozempic is approved for type 2 diabetes (max 2mg/week), while Wegovy is approved for weight management (max 2.4mg/week). Same molecule, different approved doses and indications.

How long does it take for semaglutide to work?

Appetite reduction is often noticed within 1-2 weeks. Significant weight loss typically becomes apparent by weeks 4-8. Full effects are seen at maintenance dose after 16-20 weeks.

Is oral semaglutide (Rybelsus) as effective as injectable?

Oral semaglutide is effective for diabetes but produces less weight loss than injectable. The maximum oral dose (14mg daily) produces approximately 10% weight loss vs 15-17% for injectable 2.4mg.