What is GLP-1? Basics and safety

GLP-1 receptor agonists are a class of prescription medications that mimic a naturally occurring gut hormone called glucagon-like peptide-1. Originally developed for type 2 diabetes, several of these drugs now carry FDA-approved indications for chronic weight management. They work through multiple physiological pathways — slowing gastric emptying, signaling satiety in the hypothalamus, and modulating insulin and glucagon secretion — which together reduce caloric intake and support sustained weight loss when paired with diet and exercise.

The incretin pathway: how GLP-1 drugs actually work

When you eat, your gut releases incretin hormones including native GLP-1. These hormones stimulate insulin release, suppress glucagon, and signal the brain that food has arrived. The problem is that native GLP-1 is broken down by the enzyme DPP-4 within minutes. GLP-1 receptor agonists are engineered to resist DPP-4 degradation, which extends their half-life from minutes to days, allowing once-weekly dosing.

Semaglutide, the active ingredient in Wegovy and Ozempic, is a pure GLP-1 receptor agonist with 94% structural similarity to human GLP-1. Tirzepatide, the active ingredient in Zepbound and Mounjaro, takes a different approach — it is a dual GIP/GLP-1 receptor agonist that activates both the glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 pathways simultaneously. In head-to-head trials, tirzepatide has shown numerically greater weight loss, though direct clinical comparisons for the weight-management indications are still limited.

FDA-approved GLP-1 medications for weight management

As of early 2026, four GLP-1-based medications hold FDA approval specifically for chronic weight management in adults. Wegovy (semaglutide) is available as both a 2.4 mg weekly injection (approved June 2021) and a 25 mg daily pill (approved December 2025, the first oral GLP-1 for weight loss). Zepbound (tirzepatide) was approved in November 2023 as a weekly injection at doses up to 15 mg. Saxenda (liraglutide 3.0 mg daily injection) was approved in December 2014, with a generic version from Teva becoming available in August 2025. The newest entry is Foundayo (orforglipron), an oral non-peptide GLP-1 from Eli Lilly approved in April 2026 — notable because it has no food or water timing restrictions, unlike oral Wegovy.

Each injectable also has a separate brand name approved for type 2 diabetes — Ozempic, Mounjaro, and Victoza respectively — at different doses and with different approved uses. Using a diabetes-indicated drug off-label for weight loss may affect insurance coverage, prescribing information applicability, and the monitoring protocol a clinician follows.

Clinical trial results: what the data shows

The pivotal STEP trials for semaglutide 2.4 mg demonstrated mean weight loss of approximately 14.9% of body weight over 68 weeks versus 2.4% with placebo (STEP 1, New England Journal of Medicine, 2021). Oral semaglutide 25 mg showed 16.6% weight loss at 64 weeks in the OASIS 4 trial. For tirzepatide, the SURMOUNT-1 trial showed mean weight loss of 16.0% at 5 mg, 21.4% at 10 mg, and 22.5% at 15 mg over 72 weeks versus 3.1% with placebo.

In the head-to-head SURMOUNT-5 trial comparing the two leading drugs directly, tirzepatide 15 mg achieved 20.2% weight loss versus 13.7% for semaglutide 2.4 mg. Foundayo (orforglipron) showed 12.4% weight loss at its maximum dose over 72 weeks. These are population averages — individual responses vary substantially based on dose, adherence, concurrent lifestyle changes, and genetic factors.

How telehealth GLP-1 programs typically work

Most telehealth programs follow a similar sequence: an online intake questionnaire, asynchronous or synchronous clinician review, prescription issuance if appropriate, medication delivery, and ongoing dose-escalation management with periodic check-ins.

• Intake: height, weight, BMI calculation, medical history, current medications, allergies, thyroid and pancreatic history, pregnancy status, prior weight-management attempts.

• Clinician review: a licensed provider (physician, NP, or PA) evaluates the intake, checks contraindications, and determines whether GLP-1 therapy is appropriate. Some programs require synchronous video visits; others use asynchronous chart review.

• Prescription and fulfillment: medication is dispensed through a licensed pharmacy (retail, mail-order, or compounding). Cold-chain shipping is required for injectable formulations.

• Dose escalation: treatment starts at a low dose and increases every 4 weeks to reduce GI side effects. The full escalation to maintenance dose typically takes 16-20 weeks for semaglutide and 20-32 weeks for tirzepatide.

• Ongoing monitoring: periodic check-ins to assess tolerability, adjust dosing, review labs if needed, and evaluate whether to continue, pause, or transition treatment.

Brand versus compounded GLP-1s: a critical distinction

Branded products like Wegovy and Zepbound are manufactured under FDA oversight with standardized potency, sterility, and stability testing. Compounded semaglutide and tirzepatide are prepared by compounding pharmacies under either Section 503A (patient-specific prescriptions) or Section 503B (outsourcing facilities) of the Federal Food, Drug, and Cosmetic Act.

The FDA has issued multiple warnings about compounded GLP-1 products, citing 605 adverse event reports tied to compounded semaglutide and 545 reports for compounded tirzepatide as of mid-2025. Reported problems include dosing errors (patients accidentally administering 5-20x the intended dose due to syringe confusion), sterility failures causing severe infections, and the use of salt forms such as semaglutide sodium that are chemically different from the active ingredient in approved products. When the FDA removed semaglutide from its drug shortage list in February 2025, the enforcement discretion period for compounders ended by May 2025, and compounding is now legally restricted to specific documented medical exceptions.

Questions to ask before choosing a provider

• Which specific medication do you prescribe — branded, compounded, or both? If compounded, through which pharmacy and under what regulatory framework?

• What does the monthly cost include? Separate out clinician fees, medication cost, shipping, lab work, and any membership charges.

• How does dose escalation work? What happens if I experience side effects that require slowing the titration schedule?

• What clinical oversight is provided? Is there a licensed prescriber available for questions between scheduled visits?

• What happens if treatment is not appropriate for me after the intake? Is there a refund policy?

• Do you accept insurance, and if so, which plans? If cash-pay, what is the total out-of-pocket cost for the first 3 months including all fees?