GLP-1 Receptor Agonist
What is Semaglutide?
Semaglutide is Novo Nordisk's FDA-approved GLP-1 receptor agonist, sold as Ozempic (for type 2 diabetes) and Wegovy (for weight loss). The STEP 1 trial showed 14.9% average weight loss at 68 weeks on the 2.4mg dose.
15%
Avg Weight Loss
~7 days
Half-Life
1
Receptor Target
FDA ✓
Approved
Ozempic
FDA-approved for type 2 diabetes (Dec 2017)
Max dose: 2mg weekly. Often prescribed off-label for weight loss.
Wegovy
FDA-approved for chronic weight management (Jun 2021)
Maintenance dose: 2.4mg weekly, 7.2mg maximum. Higher dose formulation for obesity.
Rybelsus
FDA-approved for type 2 diabetes (Sep 2019)
Oral tablet: originally 3mg, 7mg, or 14mg daily. As of 2026 these strengths were reformulated and renamed as the Ozempic pill (1.5/4/9mg, type 2 diabetes, US launch May 4 2026). A higher-dose Wegovy pill (25mg) was FDA-approved for weight management in December 2025, so semaglutide is no longer injectable-only.
Semaglutide Resources
Interactive Tools
Dose Calculator & Plotter
TOOLVisualize semaglutide levels, track steady state, plan your titration with our free tool.
Units Calculator
TOOLConvert any semaglutide mg dose into exact insulin syringe units for your vial concentration.
Cost Calculator
TOOLEnter your vial price to see semaglutide cost per mg, week, month, and year.
Ozempic Calculator
TOOLOzempic-specific calculator for diabetes patients (max 2mg).
Wegovy Calculator
TOOLWegovy-specific calculator for weight management (up to 2.4mg).
Guides & Articles
Reconstitution Guide
Step-by-step guide to mixing compounded semaglutide powder with bacteriostatic water.
Complete Dosing Guide
Clinical trial titration schedules, STEP trial data, side effects, and best practices.
Microdosing Guide
Split dosing strategies for better tolerability. Reduce nausea while maintaining efficacy.
Side Effects Guide
Common and serious side effects of Ozempic, Wegovy & Rybelsus. STEP/SUSTAIN trial data and tips.
Ozempic vs Wegovy
Same molecule, different doses & indications. Compare dosing, weight loss, side effects, and insurance coverage.
Compounded Semaglutide Guide
Cost-effective compounded options: sourcing, quality, dosing, and comparison vs brand-name Ozempic/Wegovy.
Retatrutide vs Semaglutide
How does semaglutide compare to the next-generation triple-agonist? Clinical data, mechanisms, and availability.
Tirzepatide vs Semaglutide
Dual-agonist vs GLP-1 only: comparing weight loss, side effects, and clinical trial outcomes.
What Is Semaglutide?
Semaglutide is a GLP-1 receptor agonist used to treat type 2 diabetes and obesity.
Semaglutide Weight Loss
How much weight can you lose on semaglutide? STEP 1 trial data shows 14.9% mean body weight loss at 68 weeks.
How Does Semaglutide Work?
Semaglutide mimics a natural gut hormone to reduce hunger, slow digestion, and signal the brain to stop eating.
How Semaglutide Works
Semaglutide is a GLP-1 receptor agonist that mimics the natural hormone GLP-1, which is released after eating. It has more long-term clinical data than any other GLP-1 weight loss medication. For a detailed look at the biology, see our how semaglutide works explainer.
What GLP-1 Does
Reduces Appetite
Acts on brain receptors to decrease hunger and increase satiety.
Slows Gastric Emptying
Food stays in stomach longer, helping you feel full.
Improves Insulin Sensitivity
Helps your body use insulin more effectively.
Reduces Glucagon
Lowers blood sugar by reducing liver glucose output.
Dosing Schedule
📋 Two dosing approaches: The schedule below is the FDA-approved clinical trial protocol from the STEP trials. Many users prefer microdosing (split dosing) for better tolerability, especially those using compounded semaglutide.
The standard titration approach starts at 0.25mg and increases every 4 weeks to minimize gastrointestinal side effects. This is the protocol used in Novo Nordisk's STEP clinical trials. See our complete dosing guide for extended protocol details.
| Weeks | Weekly Dose | Notes |
|---|---|---|
| 1-4 | 0.25mg | Starting dose |
| 5-8 | 0.5mg | First increase |
| 9-12 | 1mg | Therapeutic dose (Ozempic max for some) |
| 13-16 | 1.7mg | Wegovy titration continues |
| 17+ | 2.4mg | Recommended Wegovy maintenance (7.2mg maximum) |
Prefer Microdosing?
Many users split their weekly dose into 2-3 smaller injections for smoother drug levels and fewer side effects. This is especially popular with compounded semaglutide users.
Read the Microdosing Guide →STEP Trial Results
Semaglutide's weight loss results come from the STEP program: five large randomised trials run by Novo Nordisk between 2018 and 2022. STEP stands for Semaglutide Treatment Effect in People with obesity. The trials covered different populations and contexts, so the numbers vary, but the headline finding is consistent: at the 2.4mg weekly dose, participants lost roughly 15% of their starting body weight by week 68.
| Trial | Population | Duration | Weight Loss (sema vs placebo) |
|---|---|---|---|
| STEP 1 | Adults with obesity (no T2D), n=1,961 | 68 weeks | −14.9% vs −2.4% |
| STEP 2 | Adults with obesity + type 2 diabetes, n=1,210 | 68 weeks | −9.6% vs −3.4% |
| STEP 3 | Obesity + intensive behavioural therapy, n=611 | 68 weeks | −16.0% vs −5.7% |
| STEP 4 | Continued treatment vs switched to placebo after 20 weeks | 68 weeks | −18.2% continued vs +6.9% weight regain on placebo |
| STEP 5 | Adults with obesity (no T2D), longer-term, n=304 | 104 weeks | −15.2% vs −2.6% |
STEP 4 is the weight regain trial. Participants who stopped semaglutide after 20 weeks regained most of the weight within a year, about two thirds of what they had lost. This is why most clinicians treat semaglutide as an ongoing medication rather than a short course.
📅 SELECT Trial 2024: Cardiovascular Benefit
In March 2024, the FDA approved an expanded label for Wegovy based on the SELECT trial, a 17,604-patient study in people with established cardiovascular disease who did not have diabetes. Participants taking 2.4mg semaglutide weekly had a 20% lower risk of major cardiovascular events (heart attack, stroke, or cardiovascular death) compared to placebo over a median follow-up of 3.3 years.
This makes semaglutide the first weight loss drug to demonstrate a direct cardiovascular benefit in a large, randomised trial. The SELECT finding shifted how cardiologists approach obesity treatment, and it significantly broadened the population that qualifies for Wegovy coverage.
17,604
Participants
−20%
Cardiovascular Risk Reduction
3.3 yrs
Median Follow-Up
Half-Life & Steady State
Semaglutide has a half-life of approximately 7 days (168 hours), the longest of any GLP-1 medication. This is what makes once-weekly dosing possible and keeps blood levels relatively stable. Steady state takes about 4-5 weeks.
💡 Pro tip: Use our semaglutide calculator to visualize how your drug levels build over time and predict when you'll reach steady state.
Common Side Effects
Most Common (>5%)
- Nausea (especially during titration)
- Diarrhea
- Vomiting
- Constipation
- Abdominal pain
- Headache
Less Common
- Injection site reactions
- Fatigue
- Dizziness
- Hypoglycemia (with other diabetes meds)
- Hair thinning (with rapid weight loss)
If side effects are severe, consider microdosing or staying at your current dose longer before increasing. For a full breakdown of STEP trial data, see the semaglutide side effects guide.
Plan Your Semaglutide Protocol
Use our free calculator to plan your titration and visualize how drug levels build over time.
Frequently Asked Questions
Is semaglutide FDA-approved for weight loss?
Yes. Semaglutide is FDA-approved for weight management as Wegovy (2.4mg weekly), approved in June 2021. Ozempic (up to 2mg weekly) is approved specifically for type 2 diabetes, though physicians frequently prescribe it off-label for weight loss.
How much weight can you lose on semaglutide?
The STEP 1 trial showed an average of 14.9% body weight loss at 68 weeks on 2.4mg weekly semaglutide. Results vary: around one third of participants lost more than 20% of their body weight, while others responded less strongly. See our semaglutide weight loss guide for a breakdown by dose and population.
What is the difference between Ozempic, Wegovy, and Rybelsus?
All three contain semaglutide. Ozempic (up to 2mg weekly, injected) is approved for type 2 diabetes. Wegovy (2.4mg weekly, injected) is approved for chronic weight management. Rybelsus (3mg, 7mg, or 14mg daily tablets) was the original oral form for type 2 diabetes; as of 2026 those strengths were reformulated and renamed as the Ozempic pill (1.5/4/9mg), and a separate Wegovy pill (25mg) is the oral option for weight management. The active molecule is the same across all of them; what changes is the dose, the delivery method, and the approved indication.
How long does it take for semaglutide to start working?
Most people notice reduced appetite within the first 1-2 weeks. Measurable weight loss typically becomes visible by weeks 4-8. Drug levels reach steady state after about 4-5 weeks of weekly dosing, which is when the full appetite-suppressing effect stabilises. Use our semaglutide calculator to see how levels build over your specific schedule.
How does semaglutide compare to tirzepatide?
Tirzepatide (Mounjaro/Zepbound) targets both GLP-1 and GIP receptors, while semaglutide targets GLP-1 only. Head-to-head data suggest tirzepatide produces greater average weight loss (up to ~22% in the SURMOUNT trials vs ~15% for semaglutide in STEP 1). Both are weekly injections with similar side effect profiles. Individual response varies considerably. See the full tirzepatide vs semaglutide comparison.
What happens if you stop taking semaglutide?
The STEP 4 trial showed that participants who stopped semaglutide after 20 weeks regained most of their lost weight within a year, about two thirds of it. Appetite returns as drug levels fall, roughly 5-6 weeks after the last dose. Most clinicians treat semaglutide as an ongoing medication rather than a finite course for sustained weight management.
Is compounded semaglutide the same as Ozempic or Wegovy?
Compounded semaglutide contains the same active molecule but is produced by compounding pharmacies under different quality-control standards than FDA-approved products. It is generally much cheaper and typically requires reconstitution from a powder. See our compounded semaglutide guide for a full comparison.