What does a GLP-1 receptor agonist actually do?
GLP-1 (glucagon-like peptide-1) is an incretin hormone produced in the gut in response to food intake. It travels to several target tissues and sets off a coordinated response: the pancreas increases insulin secretion and decreases glucagon, gastric emptying slows, and the brain receives satiety signals that reduce appetite.
GLP-1 receptor agonists (GLP-1 RAs) are synthetic molecules designed to activate the same receptor as endogenous GLP-1 but with a longer half-life than the natural hormone, which breaks down within minutes. That extended activity is what makes once-weekly injectable formulations possible.
Which GLP-1 receptor agonists are FDA-approved?
The following drugs have received FDA approval. Indications and approved uses vary — some are approved for type 2 diabetes management, some for chronic weight management, and some for both. None of these branded products are compounded medications; they are manufactured drugs subject to full FDA approval requirements.
| Drug (brand) | Active ingredient | Receptor target | Dosing schedule | Primary indication |
|---|---|---|---|---|
| Ozempic / Wegovy / Rybelsus | Semaglutide | GLP-1 | Weekly (inj) / Daily (oral) | T2D; weight management |
| Mounjaro / Zepbound | Tirzepatide | GLP-1 + GIP (dual) | Weekly (inj) | T2D; weight management |
| Victoza / Saxenda | Liraglutide | GLP-1 | Daily (inj) | T2D; weight management |
| Trulicity | Dulaglutide | GLP-1 | Weekly (inj) | T2D; CV risk reduction |
| Byetta / Bydureon | Exenatide | GLP-1 | Twice daily / Weekly (inj) | T2D |
| Compounded semaglutide | Semaglutide | GLP-1 | Weekly (inj) | 503A compounded — not FDA-approved |
| Compounded tirzepatide | Tirzepatide | GLP-1 + GIP (dual) | Weekly (inj) | 503A compounded — not FDA-approved |
Semaglutide
Semaglutide is a GLP-1 receptor agonist available under three branded names: Ozempic (subcutaneous injection, approved for type 2 diabetes and cardiovascular risk reduction), Wegovy (subcutaneous injection, approved for chronic weight management), and Rybelsus (oral tablet, approved for type 2 diabetes). Semaglutide is a weekly injection in its injectable forms; Rybelsus is taken daily.
Tirzepatide (dual GIP/GLP-1 agonist)
Tirzepatide is technically a dual agonist — it activates both the GLP-1 receptor and the glucose-dependent insulinotropic polypeptide (GIP) receptor. Branded as Mounjaro (approved for type 2 diabetes) and Zepbound (approved for chronic weight management), tirzepatide is a once-weekly subcutaneous injection. In head-to-head clinical comparisons, tirzepatide has generally shown greater average weight reduction than semaglutide, though individual responses vary meaningfully.
Liraglutide
Liraglutide was the first GLP-1 RA to receive weight management approval in the US. Branded as Victoza (type 2 diabetes) and Saxenda (chronic weight management), liraglutide requires daily injections and generally produces more modest weight reduction than semaglutide or tirzepatide. It has the longest safety track record of the class.
Dulaglutide
Branded as Trulicity and approved for type 2 diabetes and cardiovascular risk reduction. Once-weekly subcutaneous injection. Not currently approved for weight management as a primary indication.
Exenatide
The first GLP-1 RA to reach clinical use. Available as Byetta (twice-daily injection) and Bydureon (weekly extended-release injection). Approved for type 2 diabetes. The twice-daily dosing requirement of Byetta has largely been superseded by more convenient weekly options in clinical practice.
The class’s key fork: semaglutide activates the GLP-1 receptor alone, while tirzepatide engages both GLP-1 and GIP — the dual mechanism behind its larger average weight reduction.
Compounded GLP-1 peptides: semaglutide and tirzepatide
When FDA-listed drug shortages exist for a branded product, compounding pharmacies operating under Section 503A of the Federal Food, Drug, and Cosmetic Act may legally prepare compounded versions for individual patients with a clinician’s prescription. Semaglutide and tirzepatide have both appeared on FDA shortage lists, making clinician-prescribed compounded versions of both legally available from licensed 503A pharmacies during those shortage periods.
Important distinctions:
- Not the same product: Compounded semaglutide is not Ozempic or Wegovy, and it cannot be represented as such. It is a compounded medication containing semaglutide as the active ingredient.
- Not FDA-approved as a drug: Compounded medications are patient-specific preparations, not FDA-approved drug products. They are legal under 503A rules when prepared by a licensed pharmacy for an individual patient under a valid prescription.
- Shortage dependence: The legal basis for compounding these specific molecules is tied to FDA-recognized shortage status. Shortage status can change. A licensed clinician stays current on the regulatory landscape and can advise on access.
- 503A pharmacy sourcing: Compounded versions obtained through licensed US telehealth providers and licensed 503A pharmacies carry the quality and sterility standards of domestic pharmacy regulation. Products sourced from unregulated vendors, overseas suppliers, or gray-market channels carry significant risks — contamination, mislabeling, inaccurate dosing — and should be avoided entirely.
How do you choose between GLP-1 receptor agonist options?
The right GLP-1 receptor agonist for a given patient depends on factors that a comparison article cannot fully adjudicate: individual metabolic profile, cardiovascular history, comorbidities, dosing schedule preference, cost and coverage situation, and clinical goals. A licensed clinician’s role is to apply this class-level knowledge to the specific person in front of them.
What a good intake process surfaces:
- Goals: Weight management, metabolic support, cardiovascular risk reduction, or some combination. Different GLP-1 agents have different approved indications; a clinician matches the agent to the clinical goal.
- Tolerance history: GI side effects (nausea, vomiting, diarrhea) are the most common class effect; they are typically dose-dependent and transient but vary by individual. Gradual titration reduces their severity.
- Contraindications: Personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2 (MEN 2) are contraindications to GLP-1 RAs. These are among the items a clinical intake screens for.
You can explore the compounded semaglutide overview or the compounded tirzepatide overview for more detail on how each is prescribed through PepScribe’s clinician-supervised pathway.
Frequently asked questions
What is a GLP-1 receptor agonist?
A GLP-1 receptor agonist is a compound that activates the glucagon-like peptide-1 (GLP-1) receptor. GLP-1 is an incretin hormone naturally released from gut cells after eating. Activating its receptor slows gastric emptying, signals satiety to the brain, and modulates insulin and glucagon secretion. The result is reduced appetite and improved glycemic regulation.
What is the difference between semaglutide and tirzepatide?
Semaglutide is a selective GLP-1 receptor agonist — it activates only the GLP-1 receptor. Tirzepatide is a dual GIP/GLP-1 receptor agonist — it activates both the GLP-1 receptor and the glucose-dependent insulinotropic polypeptide (GIP) receptor. In head-to-head clinical trials, tirzepatide has generally shown greater average weight reduction, though individual response varies.
Is compounded semaglutide the same as Ozempic or Wegovy?
No. Compounded semaglutide is a medication prepared by a licensed 503A pharmacy using semaglutide as the active ingredient. It is not the same product as Ozempic or Wegovy, and it cannot be represented as FDA-approved. It is a clinician-prescribed compounded medication available under the federal drug shortage exemption and should only be obtained through a licensed telehealth provider and a licensed domestic pharmacy.
Which GLP-1 drugs are FDA-approved?
FDA-approved GLP-1 receptor agonists include semaglutide (Ozempic, Wegovy, Rybelsus), tirzepatide (Mounjaro, Zepbound — which is a dual GIP/GLP-1 agonist), liraglutide (Victoza, Saxenda), dulaglutide (Trulicity), exenatide (Byetta, Bydureon), and albiglutide (Tanzeum, discontinued in the US). Each has different indications, dosing schedules, and delivery formats.
Can I get a GLP-1 agonist without insurance?
The list price of branded GLP-1 drugs is high without insurance coverage. Clinician-prescribed compounded semaglutide or tirzepatide, available through a licensed telehealth provider and a licensed 503A pharmacy, is typically available at a fraction of the cost of branded products during periods of FDA-recognized shortage.