What Is GLP-1? Ozempic, Wegovy, and Zepbound Explained
What is GLP-1? GLP-1 (glucagon-like peptide-1) is a natural gut hormone your body releases after eating. It signals fullness, slows digestion, and helps regulate blood sugar. GLP-1 medications—like Ozempic, Wegovy, and Zepbound—are prescription drugs that activate the same pathway but last much longer.
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Medical Disclaimer: This guide is for educational purposes only—not medical advice. GLP-1 medications require a prescription and medical monitoring. Always consult a licensed clinician.
Quick Answer (Read This First)
- GLP-1 = a hormone your body makes that affects hunger and blood sugar
- GLP-1 medications = drugs that mimic that signal for much longer
- Semaglutide = a specific GLP-1 drug ingredient
- Ozempic / Wegovy / Rybelsus = brand names using semaglutide (different indications and doses)
- Tirzepatide (Zepbound / Mounjaro) = activates two pathways: GIP + GLP-1 (not just GLP-1)
The painkiller analogy (memorize this):
| Level | Painkiller Example | GLP-1 Example |
|---|---|---|
| Category | "Pain reliever" | GLP-1 medication |
| Drug ingredient | Ibuprofen | Semaglutide |
| Brand name | Advil, Motrin | Ozempic, Wegovy |
Same logic: category → ingredient → brand name.
For informational purposes only — not medical advice. Consult a licensed provider before starting any medication.
What Does GLP-1 Mean?
GLP-1 stands for glucagon-like peptide-1.
In plain English: it's one of your body's "I just ate—handle this meal" signals. After eating, GLP-1 helps:
- Increase insulin when glucose is high
- Reduce glucagon (a hormone that raises blood sugar)
- Slow stomach emptying
- Signal fullness in the brain
Pronunciation: GLP-1 = "G-L-P-one"
Natural GLP-1 vs. GLP-1 Medications
Natural GLP-1 (what your body makes)
Your body releases GLP-1 after meals, but it breaks down in minutes because an enzyme called DPP-4 inactivates it quickly. The signal is too brief to dramatically change your appetite.
GLP-1 medications (what makes them different)
GLP-1 medications are engineered to:
- Last longer (days instead of minutes)
- Produce a more consistent fullness signal
- Help sustain a reduced-calorie pattern more easily
The simplest way to think about it: Natural GLP-1 is a quick text message. A GLP-1 medication is a repeating calendar reminder.
All GLP-1 Medications Compared
Not every "GLP-1" you hear about is used for weight loss, and not every weight-loss medication is GLP-1 only.
| Brand Name | Active Ingredient | Pathway | Form | FDA-Approved For |
|---|---|---|---|---|
| Wegovy | Semaglutide | GLP-1 | Weekly injection | Chronic weight management; CV risk reduction |
| Wegovy tablets | Semaglutide | GLP-1 | Daily tablet | Chronic weight management; CV risk reduction (adults only) |
| Ozempic | Semaglutide | GLP-1 | Weekly injection | Type 2 diabetes (often used off-label for weight) |
| Rybelsus | Semaglutide | GLP-1 | Daily tablet | Type 2 diabetes |
| Zepbound | Tirzepatide | GIP + GLP-1 | Weekly injection | Chronic weight management; moderate-to-severe OSA in adults with obesity |
| Mounjaro | Tirzepatide | GIP + GLP-1 | Weekly injection | Type 2 diabetes |
| Saxenda | Liraglutide | GLP-1 | Daily injection | Chronic weight management |
| Victoza | Liraglutide | GLP-1 | Daily injection | Type 2 diabetes |
| Trulicity | Dulaglutide | GLP-1 | Weekly injection | Type 2 diabetes |
Important: FDA indications vary. Your clinician decides what's appropriate for you.
Yes. Ozempic contains semaglutide, which is a GLP-1 receptor agonist. However, Ozempic is FDA-approved for Type 2 diabetes—not weight loss. When someone says "I'm on Ozempic for weight loss," they're using it off-label.
Same ingredient (semaglutide), different products.
Wegovy vs Ozempic Comparison
| Wegovy | Ozempic | |
|---|---|---|
| Drug | Semaglutide | Semaglutide |
| FDA-approved for | Chronic weight management (and CV risk reduction) | Type 2 diabetes (and CV/kidney risk reduction) |
| Maximum dose | 2.4 mg weekly (injection) or 25 mg daily (tablets) | 2 mg weekly |
| Available forms | Injection AND tablets (as of 2025) | Injection only |
Why Does Tirzepatide (Zepbound) Cause More Weight Loss?
Tirzepatide activates two pathways: GIP + GLP-1 (not GLP-1 alone).
In head-to-head trials, tirzepatide produces greater average weight loss. The simplest explanation:
- Semaglutide = strong GLP-1 signal
- Tirzepatide = GLP-1 signal plus GIP signal, which may enhance metabolic and appetite effects
This doesn't mean "tirzepatide is always better." The best choice depends on your medical history, side effect tolerance, insurance coverage, and goals.
How Do GLP-1 Medications Work for Weight Loss?
Most people experience weight loss through four overlapping effects:
People often report fewer intrusive thoughts about food and reduced urge-driven snacking.
You feel satisfied with smaller portions.
Food stays in your stomach longer, extending satiety. (This also explains the nausea—more on that below.)
More stable glucose can reduce hunger swings, especially for people with insulin resistance.
How Much Weight Loss Is Typical?
Clinical trial results vary by medication and dosage:
STEP 1 Trial
−14.9%
Average body weight loss over 68 weeks (vs 2.4% with placebo)
SURMOUNT-1 Trial
−20.9%
Average body weight loss at max dose (15mg) over 72 weeks
Head-to-head data (SURMOUNT-5, 2025): Tirzepatide produced −20.2% mean weight loss vs −13.7% with semaglutide at 72 weeks.
GLP-1 Side Effects
The mechanism that makes you feel satisfied is the same mechanism that can cause GI symptoms. They're two sides of the same coin. For a comprehensive breakdown, see our complete guide to GLP-1 cons and risks.
Common Side Effects (from FDA labels)
| Side Effect | Wegovy (injection) | Zepbound |
|---|---|---|
| Nausea | ~44% | 25-29% |
| Diarrhea | ~30% | 19-23% |
| Vomiting | ~25% | 8-13% |
| Constipation | ~24% | 17-21% |
Side effects typically peak during dose increases and often improve after 4-6 weeks.
Serious Side Effects
| Condition | Warning Signs | What to Do |
|---|---|---|
| Pancreatitis | Severe abdominal pain radiating to back, vomiting | Stop medication, seek emergency care |
| Gallbladder problems | Upper right abdominal pain, jaundice | Contact provider promptly |
| Hypoglycemia (with other diabetes meds) | Shakiness, confusion, sweating | Treat with glucose, contact provider |
| Kidney problems | Decreased urination, swelling | Contact provider promptly |
| Allergic reactions | Rash, swelling, difficulty breathing | Seek emergency care if severe |
| Aspiration risk (anesthesia/sedation) | GLP-1 meds slow gastric emptying; food may remain in stomach | Tell your surgical/anesthesia team before any procedure |
Who Qualifies for GLP-1 Medications?
FDA-approved GLP-1 weight-loss medications (Wegovy, Zepbound) require:
- BMI ≥30 (obesity), or
- BMI ≥27 (overweight) with at least one weight-related condition (high blood pressure, type 2 diabetes, high cholesterol, etc.)
Clinicians also consider your medical history, current medications, and contraindications (like personal/family history of medullary thyroid cancer or MEN2 syndrome).
Pills vs. Injections (Wegovy Tablets)
As of 2025, Wegovy is available in both injection and tablet form.
Approved for adults and adolescents 12+ with obesity. Inject once weekly at any time of day.
Adults only. Take once daily.
Why pills aren't necessarily "easier"
Oral semaglutide has strict timing requirements:
- • Take on an empty stomach (first thing in the morning)
- • Swallow with a small amount of plain water only (no more than 4 oz)
- • Wait at least 30 minutes before eating, drinking, or taking other medications
Some people find a once-weekly injection more convenient than a daily pill with these restrictions.
Titration Schedules
All GLP-1 medications start at a low dose and gradually increase to minimize side effects. Here are the standard schedules:
Wegovy Injection
| Period | Dose |
|---|---|
| Weeks 1-4 | 0.25 mg weekly |
| Weeks 5-8 | 0.5 mg weekly |
| Weeks 9-12 | 1.0 mg weekly |
| Weeks 13-16 | 1.7 mg weekly |
| Weeks 17+ | 2.4 mg weekly (maintenance) |
Wegovy Tablets
| Period | Dose |
|---|---|
| Days 1-30 | 1.5 mg daily |
| Days 31-60 | 4 mg daily |
| Days 61-90 | 9 mg daily |
| Days 91+ | 25 mg daily (maintenance) |
Zepbound (Tirzepatide)
| Period | Dose |
|---|---|
| Weeks 1-4 | 2.5 mg weekly |
| Weeks 5+ | 5 mg weekly, then increase by 2.5 mg every 4+ weeks |
| Maintenance | 5, 10, or 15 mg weekly (max 15 mg) |
Your clinician may adjust the schedule based on tolerability.
What Happens If You Stop?
Most people regain weight after stopping GLP-1 medications.
STEP 1 extension data: Participants regained approximately two-thirds of prior weight loss within one year after stopping semaglutide.
This reflects biology, not failure. Obesity is often a chronic condition that may require long-term treatment—similar to medications for high blood pressure or diabetes.
Discuss a long-term plan with your clinician before starting treatment.
Keeping Muscle While Losing Weight
Rapid weight loss—from any method—can include loss of lean mass (muscle). Research suggests 25-40% of weight lost may be lean mass rather than fat.
What helps preserve muscle:
- Protein intake: Aim for 0.7-1g per pound of body weight daily
- Resistance training: 2-3 sessions per week
- Gradual calorie deficits: Avoid extreme restriction
Talk to your clinician about strategies to minimize muscle loss during treatment.
Compounded Semaglutide Safety
Critical facts about compounded semaglutide
Compounded semaglutide is custom-mixed by specialized pharmacies. It's significantly cheaper ($200-500/month vs. $1,000+) because it's not the brand-name product.
- Not FDA-approved: Compounded versions haven't been through FDA review for safety and efficacy
- Quality varies: FDA has warned about dosing errors and some compounders using "semaglutide salts" (which may not have the same properties as FDA-approved semaglutide)
- Legal status changes: Compounding rules depend on FDA shortage declarations and enforcement policies
If you're considering compounded options, see our guide on how to get GLP-1 safely and avoid scams.
Questions to Ask Your Doctor
Bring these questions to your consultation:
- Based on my medical history, which GLP-1 medication is appropriate for me?
- Will my insurance cover this medication?
- What side effects should I expect, and how should I manage them?
- What's the long-term plan if I want to stop the medication?
- How will we monitor my progress and adjust treatment?
- Are there any interactions with my current medications?
Frequently Asked Questions
Glossary
| Term | Plain-English Definition |
|---|---|
| GLP-1 | Glucagon-like peptide-1 — a gut hormone that regulates appetite and blood sugar |
| GLP-1 agonist / GLP-1 RA | A medication that activates GLP-1 receptors |
| Incretin | A category of gut hormones that affect insulin secretion; GLP-1 is one type |
| GIP | Another incretin hormone; tirzepatide activates both GIP and GLP-1 receptors |
| Semaglutide | A GLP-1 drug ingredient (used in Ozempic, Wegovy, Rybelsus) |
| Tirzepatide | A dual GIP/GLP-1 drug ingredient (used in Mounjaro, Zepbound) |
| Titration | Gradually increasing medication dose over time to improve tolerability |
| Off-label | Using an FDA-approved medication for a purpose not listed on its FDA label |
| Prior authorization | Insurance requirement for documentation before covering a medication |
| Compounding | Custom preparation of medication by a specialized pharmacy (not the same as FDA-approved products) |
| MTC | Medullary thyroid carcinoma — a type of thyroid cancer mentioned in GLP-1 warnings |
| MEN 2 | Multiple Endocrine Neoplasia syndrome type 2 — an inherited condition that's a contraindication for GLP-1 medications |
| BMI | Body mass index — a measure of weight relative to height used in eligibility criteria |
| Gastric emptying | How quickly food leaves your stomach; GLP-1 medications slow this process |
Sources and Editorial Standards
This guide was created by reviewing FDA prescribing information for all medications discussed, published clinical trial data, FDA safety communications, and peer-reviewed research. It's written for accuracy and clarity, not to promote any specific medication or provider.