Ozempic (Semaglutide) — Complete Guide for 2026
- Ozempic (semaglutide) is a GLP-1 receptor agonist — originally approved for Type 2 diabetes
- It produces average weight loss of 15–17% of body weight over 68 weeks (STEP trials)
- The most common side effects are nausea, vomiting, and constipation — usually mild and temporary
- It works by slowing gastric emptying, reducing appetite, and improving insulin secretion
- Ozempic is licensed for Type 2 diabetes; Wegovy (same drug, higher dose) is licensed for obesity
What Is Semaglutide (Ozempic/Wegovy)?
Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist — a medication that mimics a hormone naturally produced in the gut after eating. It was first approved for Type 2 diabetes management (brand name Ozempic, weekly injection) and later at a higher dose for chronic weight management (brand name Wegovy). Oral semaglutide (Rybelsus) is also available for diabetes.
How Ozempic Works
1. Reduces Appetite
GLP-1 receptors in the brain (hypothalamus) signal satiety. Semaglutide activates these receptors continuously, producing a profound and sustained reduction in appetite — most people report thinking about food significantly less, having smaller portions, and stopping eating sooner.
2. Slows Gastric Emptying
Food leaves the stomach more slowly, extending the feeling of fullness after meals and reducing post-meal blood glucose spikes.
3. Improves Insulin Secretion
Stimulates insulin release in response to glucose (glucose-dependent), reduces glucagon secretion, and improves insulin sensitivity — addressing the core defects in Type 2 diabetes.
Weight Loss Evidence — STEP Trials
The STEP programme compared semaglutide 2.4mg weekly (Wegovy) to placebo in adults with obesity:
| Trial | Participants | Weight Loss (semaglutide) | Weight Loss (placebo) |
|---|---|---|---|
| STEP 1 (no diabetes) | 1,961 | 14.9% | 2.4% |
| STEP 2 (Type 2 diabetes) | 1,210 | 9.6% | 3.4% |
| STEP 3 (intensive lifestyle) | 611 | 16.0% | 5.7% |
| SELECT (cardiovascular) | 17,604 | ~10% + 20% CVD reduction | Placebo |
Managing Side Effects
- Nausea: Start at lowest dose, eat smaller meals, avoid fatty/spicy food, do not lie down after eating
- Constipation: Increase fibre, fluid intake, and physical activity
- Vomiting: Eat slowly, avoid large portions, cold foods may be better tolerated
- The 'medication face': Rapid facial fat loss — a cosmetic concern, not a medical risk