GLP-1 Medications for Weight Loss: Semaglutide, Tirzepatide, and What You Need to Know

What are GLP-1 medications?

GLP-1 medications are a class of drugs called glucagon-like peptide-1 receptor agonists. They mimic a natural hormone produced in the gut that regulates appetite, blood sugar, and digestion. Originally developed to treat type 2 diabetes, they have become the most effective pharmaceutical tools for weight management available today. Cora Health providers prescribe compounded versions of two GLP-1 medications — semaglutide and tirzepatide — through its network of board-certified providers and US-licensed 503A compounding pharmacies.

The FDA-approved brand-name versions include Ozempic and Wegovy (semaglutide, manufactured by Novo Nordisk) and Mounjaro and Zepbound (tirzepatide, manufactured by Eli Lilly). Compounded versions of these medications are prepared by state-licensed compounding pharmacies and are not FDA-approved. They are not therapeutically equivalent to the brand-name products.

Despite that distinction, GLP-1 medications as a class have more clinical trial data supporting their effectiveness for weight loss than any other pharmaceutical intervention in the history of obesity medicine. Understanding what they are, how they differ, and what the evidence says is the first step toward an informed conversation with a provider.

How do GLP-1 medications cause weight loss?

GLP-1 receptor agonists work through three interconnected mechanisms. First, they act on the hypothalamus to reduce appetite. Patients consistently report feeling less hungry, getting full faster, and experiencing fewer cravings — particularly for high-calorie, high-fat foods. Second, they slow gastric emptying, which means food stays in the stomach longer, extending the feeling of fullness after meals. Third, they improve insulin sensitivity and glucose regulation, which reduces the metabolic dysfunction that often accompanies obesity.

Semaglutide activates GLP-1 receptors only. Tirzepatide is a dual agonist — it activates both GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors. The GIP pathway adds an additional mechanism for fat metabolism and appetite regulation, which may explain why tirzepatide produces somewhat greater weight loss in clinical trials.

Both medications are administered as once-weekly subcutaneous injections. Treatment starts at a low dose and increases gradually over several weeks to minimize gastrointestinal side effects. This titration period is important — skipping it or accelerating it typically leads to worse tolerability without better outcomes.

Semaglutide vs tirzepatide: how do they compare?

This is the question patients ask most often, and the honest answer is that both are highly effective. The differences are real but narrower than marketing might suggest. Your provider is the right person to determine which medication fits your health profile.

Semaglutide has been studied longer and has more published long-term data. The STEP trial program (2021-2022) demonstrated consistent weight loss of 14.9% over 68 weeks, sustained at 15.2% over two years. The SELECT trial (2023) demonstrated a 20% reduction in major cardiovascular events in patients with obesity. Semaglutide has a single mechanism of action (GLP-1 receptor agonism).

Tirzepatide is newer and has shown higher average weight loss in clinical trials. The SURMOUNT-1 trial (Jastreboff et al., New England Journal of Medicine, 2022) demonstrated weight loss of 16.0% at the 5mg dose, 21.4% at 10mg, and 22.5% at 15mg over 72 weeks. 96% of participants on the highest dose lost at least 5% of their body weight. Tirzepatide's dual mechanism (GLP-1 + GIP agonism) may account for the higher efficacy numbers.

Side effect profiles are similar for both drugs. Nausea, vomiting, diarrhea, and constipation are the most common adverse effects, particularly during dose escalation. The SURMOUNT trials reported gastrointestinal events in a similar proportion of participants as the STEP trials.

Cost differs between the two. Compounded semaglutide is generally less expensive than compounded tirzepatide. Through Cora Health, the Essential Plan (compounded semaglutide) is $120 per month and the Premium Plan (compounded tirzepatide) is $199 per month.

Direct head-to-head comparison data between semaglutide and tirzepatide is limited. Cross-trial comparisons suggest tirzepatide produces greater average weight loss, but trial populations, protocols, and endpoints differ enough that a definitive ranking is not scientifically appropriate. Individual results vary with both medications. The right medication depends on your health profile, tolerance, goals, and what your provider recommends after evaluating you.

Clinical evidence: what do the trials show?

The evidence base for GLP-1 medications is unusually strong by pharmaceutical standards. Multiple large, randomized, placebo-controlled trials have been published in top-tier medical journals. All trial data below comes from studies of FDA-approved formulations, not compounded versions. Compounded GLP-1 medications have not been independently studied in clinical trials.

For semaglutide, the STEP 1 trial (Wilding et al., New England Journal of Medicine, 2021) enrolled 1,961 adults with obesity. Semaglutide 2.4mg weekly produced 14.9% weight loss over 68 weeks versus 2.4% with placebo. The STEP 5 trial (Garvey et al., Nature Medicine, 2022) confirmed sustained weight loss of 15.2% at two years. The SELECT trial (Lincoff et al., NEJM, 2023) showed a 20% reduction in major cardiovascular events in 17,604 patients with obesity.

For tirzepatide, the SURMOUNT-1 trial (Jastreboff et al., NEJM, 2022) enrolled 2,539 adults with obesity. At the highest dose (15mg), participants lost an average of 22.5% of body weight over 72 weeks. The SURMOUNT-2 trial (Lancet, 2023) studied patients with type 2 diabetes and showed weight loss of up to 17.7% in patients with well-controlled blood sugar.

These are population averages. Individual responses vary based on starting weight, dose achieved, adherence, diet, exercise, genetics, and other factors. Some patients lose substantially more than the average, and some lose less. Your provider can help set realistic expectations based on your specific profile.

Who is a candidate for GLP-1 treatment?

GLP-1 medications are generally prescribed for adults who meet specific clinical criteria. A licensed provider evaluates each patient individually — there is no self-qualification process.

The standard clinical criteria include a BMI of 30 or higher (obesity), or a BMI of 27 or higher (overweight) with at least one weight-related health condition such as type 2 diabetes, high blood pressure, high cholesterol, or obstructive sleep apnea. Some providers may consider patients with a BMI below 27 in specific clinical circumstances, but this is less common.

• Personal or family history of medullary thyroid carcinoma (MTC) — semaglutide and tirzepatide carry a boxed warning about thyroid C-cell tumors observed in rodent studies
• Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)
• History of pancreatitis — GLP-1 medications may increase the risk of pancreatitis
• Severe gastrointestinal disease including gastroparesis
• Pregnancy or plans to become pregnant — GLP-1 medications should be discontinued at least 2 months before planned conception
• Known hypersensitivity to semaglutide, tirzepatide, or any component of the formulation

Compounded vs brand-name GLP-1 medications

Brand-name GLP-1 medications (Ozempic, Wegovy, Mounjaro, Zepbound) are FDA-approved, meaning they have undergone rigorous review for safety, efficacy, and manufacturing quality. Compounded versions have not undergone this review. Compounded medications are not FDA-approved and are not therapeutically equivalent to FDA-approved products.

The practical difference that drives most patients toward compounded options is cost. Brand-name Wegovy costs approximately $1,350 per month and Zepbound approximately $1,060 per month without insurance. Many insurance plans do not cover GLP-1 medications for weight loss, or impose prior authorization requirements that can take weeks. Compounded semaglutide typically costs $120 to $250 per month and compounded tirzepatide $199 to $350 per month, depending on the provider.

When choosing compounded medications, the quality of the compounding pharmacy matters. Patients should work with providers who partner with 503A state-licensed pharmacies that follow USP sterile compounding standards, source pharmaceutical-grade ingredients from FDA-registered suppliers, and conduct potency and sterility testing. For a deeper discussion of compounding safety, see our complete compounded semaglutide guide.

How to start GLP-1 treatment online

The process of starting GLP-1 treatment through a telehealth provider typically involves three steps: a health assessment, a provider evaluation, and pharmacy fulfillment.

First, look for a legitimate provider. Key indicators include licensed, board-certified physicians who conduct individual evaluations, a named and verifiable compounding pharmacy partner, LegitScript certification, HIPAA-compliant patient portal, transparent all-inclusive pricing with clear cancellation terms, and a process that does not guarantee a prescription before medical evaluation.

Cora Health patients complete a five-minute online health assessment, receive a provider review within 24 hours, and get their medication shipped from VialsRx, a US-licensed 503A compounding pharmacy. The Essential Plan (compounded semaglutide) starts at $120 per month and the Premium Plan (compounded tirzepatide) starts at $199 per month. Both include provider consultation, pharmacy fulfillment, and free shipping to all 50 US states.

Regardless of which provider you choose, the most important factor is that a licensed provider conducts a genuine medical evaluation before any prescription is written. GLP-1 medications are powerful drugs with real contraindications, and the evaluation process exists to protect patients.