What is a GLP-1 receptor agonist?
Glucagon-like peptide-1 (GLP-1) is an incretin hormone produced in the gut in response to food intake. It has several physiological effects: it stimulates insulin secretion in a glucose-dependent manner, suppresses glucagon release, slows gastric emptying, and acts on the hypothalamus to reduce appetite. The combination of these effects makes the GLP-1 axis a compelling therapeutic target for both type 2 diabetes and obesity.
GLP-1 receptor agonists (GLP-1 RAs) are drugs designed to mimic and amplify the effects of endogenous GLP-1. Because native GLP-1 has a very short half-life (minutes), pharmaceutical development focused on creating analogs or conjugates with much longer durations of action, enabling once-weekly or once-daily dosing.
Which FDA-approved GLP-1 drugs are available — and for what?
Multiple GLP-1 receptor agonists have received FDA approval, for different indications and dosing frequencies. Here is the factual map as of mid-2025:
| Drug (brand) | Active ingredient | FDA indication | Dosing |
|---|---|---|---|
| Wegovy | Semaglutide | Chronic weight management | 2.4 mg weekly (injectable) |
| Zepbound | Tirzepatide (GIP/GLP-1) | Chronic weight management; obstructive sleep apnea | 2.5–15 mg weekly (injectable) |
| Ozempic | Semaglutide | Type 2 diabetes; CV risk reduction | 0.5–2 mg weekly (injectable) |
| Rybelsus | Semaglutide (oral) | Type 2 diabetes only | 3–14 mg daily |
| Mounjaro | Tirzepatide (GIP/GLP-1) | Type 2 diabetes | 2.5–15 mg weekly (injectable) |
| Saxenda | Liraglutide | Chronic weight management | 3 mg daily (injectable) |
| Victoza / Trulicity / Byetta | Liraglutide / Dulaglutide / Exenatide | Type 2 diabetes only | Daily or weekly (injectable) |
Semaglutide (Ozempic, Wegovy, Rybelsus)
Semaglutide is manufactured by Novo Nordisk and available in three formulations:
- Ozempic (injectable, once weekly): Approved for type 2 diabetes and, separately, for cardiovascular risk reduction in adults with type 2 diabetes and established cardiovascular disease. Doses: 0.5 mg, 1 mg, 2 mg weekly.
- Wegovy (injectable, once weekly): Approved for chronic weight management in adults with initial BMI ≥30 (obesity) or ≥27 with at least one weight-related condition, and in adolescents age 12 and older with obesity. The approved dose for weight management is 2.4 mg weekly.
- Rybelsus (oral, daily): Approved for type 2 diabetes only. The oral formulation uses a delivery agent (SNAC) to enable GI absorption. Not approved for weight management.
Using Ozempic off-label for weight management is common in clinical practice but is not the FDA-approved application. The 2.4 mg dose in Wegovy is specific to the weight management indication.
Tirzepatide (Mounjaro, Zepbound)
Tirzepatide is manufactured by Eli Lilly and acts as a dual GIP/GLP-1 receptor agonist. GIP (glucose-dependent insulinotropic polypeptide) is the second major incretin hormone. Tirzepatide’s dual mechanism has produced larger average weight reductions in head-to-head comparisons with GLP-1-only agonists in some contexts.
- Mounjaro (injectable, once weekly): Approved for type 2 diabetes. Doses: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg weekly.
- Zepbound (injectable, once weekly): Approved for chronic weight management using the same dose range. Also received an approval for obstructive sleep apnea in adults with obesity.
Liraglutide (Victoza, Saxenda)
Liraglutide is a once-daily GLP-1 RA from Novo Nordisk. Victoza is approved for type 2 diabetes; Saxenda (3 mg daily) is approved for chronic weight management. The daily injection schedule and comparatively smaller magnitude of weight loss relative to tirzepatide and high-dose semaglutide have shifted clinical preference toward the newer weekly agents in many settings, but liraglutide remains an FDA-approved option.
Dulaglutide (Trulicity) and exenatide (Byetta, Bydureon)
Older GLP-1 RAs indicated only for type 2 diabetes. Dulaglutide is once-weekly; exenatide comes in a twice-daily immediate-release and once-weekly extended release form. Neither is approved for weight management as a primary indication, though both have been used off-label. They are generally considered less potent for weight reduction than semaglutide or tirzepatide at their respective approved doses.
The active ingredient in a compounded GLP-1 may be the same molecule as a branded drug, but the finished compounded product is not FDA-approved.
How much weight do FDA-approved GLP-1 drugs actually cause people to lose?
The evidence base supporting semaglutide and tirzepatide for weight management is substantial:
- STEP 1 trial (semaglutide 2.4 mg): In adults with obesity or overweight with a weight-related condition, semaglutide 2.4 mg weekly produced mean body weight reduction of approximately 14.9% over 68 weeks, versus approximately 2.4% with placebo. 86%of participants on active treatment achieved ≥5% body weight loss.
- SURMOUNT-1 trial (tirzepatide 5–15 mg): Participants on tirzepatide 15 mg achieved mean weight reduction of approximately 20.9% over 72 weeks, versus approximately 3.1% with placebo. These are among the largest weight reductions demonstrated by any pharmaceutical intervention short of bariatric surgery.
These trials enrolled participants without diabetes. Outcomes in individuals with type 2 diabetes are somewhat attenuated, which is consistent with the altered metabolic environment of that population.
Where do compounded semaglutide and tirzepatide fit?
Compounded semaglutide and tirzepatide contain semaglutide or tirzepatide as the active pharmaceutical ingredient, but are not themselves FDA-approved products. The distinction matters and should be stated clearly.
The practical case for compounded options is primarily economic: branded Wegovy and Zepbound can cost $1,000 or more monthly at retail without insurance coverage. Compounded versions, prepared by licensed 503A pharmacies under a valid clinician prescription, are typically available at substantially lower cost.
The regulatory window that permitted compounded tirzepatide and semaglutide during shortage periods is not permanent. Shortage status can change, and with it the legal basis for certain compounding. Patients considering compounded GLP-1 options should work with providers who monitor this landscape and can explain the current regulatory status of their specific formulation.
PepScribe’s compounded semaglutide and tirzepatide programs use licensed 503A pharmacies with US-based, transparent API sourcing. No hidden overseas supply chain. Every prescription is issued after clinician review.
What are the side effects, and who should not use GLP-1 drugs?
The most common side effects of GLP-1 receptor agonists are gastrointestinal: nausea, vomiting, diarrhea, and constipation. These effects are typically most prominent early in treatment and during dose escalation, and often diminish over time. A structured titration schedule exists precisely to minimize GI side effect burden.
More serious but rarer risks include pancreatitis, gallbladder disease, and — based on rodent data — potential thyroid C-cell effects. The thyroid risk is the basis of the absolute contraindication for individuals with a personal or family history of medullary thyroid carcinoma or MEN2. This contraindication applies to all FDA-approved GLP-1 RAs and to compounded versions as well, since the mechanism is the same.
A proper clinician evaluation screens for these contraindications before prescribing. The intake process at PepScribe includes this screening.
Frequently asked questions
What FDA-approved GLP-1 drugs are available for weight management?
As of 2024–2025, the FDA-approved GLP-1 receptor agonists specifically indicated for chronic weight management (in adults with obesity or overweight with a weight-related condition) include semaglutide 2.4 mg weekly (Wegovy) and tirzepatide 5–15 mg weekly (Zepbound). Tirzepatide is a dual GIP/GLP-1 receptor agonist. Both require clinician prescription.
Are compounded semaglutide and tirzepatide FDA-approved?
No. Compounded semaglutide and tirzepatide contain semaglutide or tirzepatide as the active pharmaceutical ingredient, but the compounded finished products are not FDA-approved. They are prepared by licensed 503A compounding pharmacies under different regulatory standards. The approval status of the branded drug does not transfer to the compounded version.
What is the difference between semaglutide for diabetes and semaglutide for weight loss?
Ozempic (semaglutide 0.5–2 mg weekly) is approved for type 2 diabetes. Wegovy (semaglutide 2.4 mg weekly) is approved for chronic weight management. Same active ingredient, different dose and indication. Rybelsus is a daily oral semaglutide formulation approved for diabetes only. Using Ozempic for weight management is off-label.
How do GLP-1 drugs work for weight management?
GLP-1 receptor agonists mimic endogenous glucagon-like peptide-1, a gut-derived incretin hormone. They slow gastric emptying (increasing satiety), reduce appetite via hypothalamic GLP-1 receptor signaling, and — in the case of tirzepatide — also activate GIP receptors. The net effect is reduced caloric intake and, in clinical trials, significant body weight reduction.
Who is not a candidate for GLP-1 drugs?
Absolute contraindications for GLP-1 receptor agonists include personal or family history of medullary thyroid carcinoma and multiple endocrine neoplasia syndrome type 2 (MEN2). Relative contraindications and cautions include pancreatitis history, severe gastrointestinal disorders, and certain pregnancy/fertility considerations. A clinician evaluation is required before prescribing.
Can I get compounded semaglutide or tirzepatide through PepScribe?
Yes. PepScribe connects patients with licensed clinicians who can evaluate candidacy for compounded semaglutide or tirzepatide through our peptide programs. All compounded products come from licensed 503A pharmacies with US-based API sourcing.