The weight loss drugs generating the most attention are a class of medications called GLP-1 receptor agonists, with Wegovy (semaglutide) and Zepbound (tirzepatide) leading the field. These injectable drugs mimic a natural gut hormone to reduce appetite and slow digestion, producing average weight loss of 15 to 21% of body weight over about 68 to 72 weeks in clinical trials. They’re not the only options available, but they represent a significant leap in effectiveness compared to older obesity medications.
How GLP-1 Drugs Work
Your small intestine naturally produces a hormone called GLP-1 after you eat. This hormone does several things at once: it triggers insulin release to manage blood sugar, slows down how quickly your stomach empties food, and signals to your brain that you’re full. In people without obesity, this system helps regulate appetite naturally. The newer weight loss drugs are synthetic versions of this hormone, binding to the same receptors and amplifying those effects.
The practical result is that people on these medications feel satisfied with smaller portions and experience less food-focused thinking between meals. Stomach emptying slows significantly, meaning food sits longer in your digestive tract and you stay full for hours after eating. This isn’t willpower in a syringe. It’s a shift in the biological signals your brain receives about hunger and fullness.
Zepbound takes this a step further. It mimics two gut hormones instead of one, targeting both GLP-1 and GIP receptors. This dual action appears to explain why it produces slightly greater weight loss in head-to-head comparisons: a 72-week course of tirzepatide (Zepbound’s active ingredient) at its maximum dose reduced body weight by 20.9% in trials, compared to 14.9% with semaglutide over 68 weeks.
The Major Drugs Available Now
Wegovy was FDA-approved for obesity treatment in 2021 and quickly became a household name. It’s a once-weekly injection of semaglutide, the same active ingredient found in the diabetes drug Ozempic, but dosed specifically for weight management. In December 2025, an oral pill version of Wegovy also received FDA approval, giving patients an alternative to injections.
Zepbound, approved for obesity in 2023, is a once-weekly injection of tirzepatide. Its diabetes counterpart is sold as Mounjaro. Because it targets two hormone pathways instead of one, it currently produces the highest average weight loss of any approved medication.
Several older medications remain on the market as well:
- Contrave (naltrexone-bupropion) is a twice-daily pill combining an opioid-blocking drug with an antidepressant. It produces more modest results, with patients losing an average of 5 to 10% of body weight.
- Qsymia (phentermine-topiramate) combines a stimulant-based appetite suppressant with a drug originally used for seizures and migraines. It’s been available since 2012.
- Saxenda (liraglutide) is a daily GLP-1 injection that preceded Wegovy but requires more frequent dosing and produces less weight loss.
- Orlistat (Xenical, or Alli over the counter) blocks fat absorption in the gut. It’s the least effective of the group but the only one available without a prescription in its lower-dose form.
- Phentermine (Adipex, Lomaira) is the oldest and most widely used weight loss drug, approved only for short-term use.
Who Qualifies for a Prescription
FDA guidelines set two main thresholds for prescribing weight loss medications. You typically qualify if your BMI is 30 or higher, which corresponds to clinical obesity. You can also qualify at a BMI of 27 or higher if you have at least one weight-related health condition, such as type 2 diabetes, high blood pressure, high cholesterol, sleep apnea, or cardiovascular disease.
These criteria apply broadly across the approved medications, though individual insurers may add their own requirements, such as documented attempts at diet and exercise or prior authorization from a specialist.
What the Dosing Process Looks Like
Both Wegovy and Zepbound follow a gradual dose escalation to minimize side effects. You don’t start at the full therapeutic dose. With semaglutide, you begin at 0.25 mg per week and increase by 0.25 mg every four weeks, reaching the target dose of 2.4 mg over roughly 16 to 20 weeks. Tirzepatide starts at 2.5 mg per week and increases in 2.5 mg increments every four weeks, up to a maximum of 15 mg.
This slow ramp-up matters because side effects tend to spike with each dose increase. Starting low gives your body time to adjust before the next step up.
Common and Serious Side Effects
Gastrointestinal problems are by far the most frequent side effects. Across GLP-1 drugs, about 21% of users experience nausea, making it the single most reported issue. Diarrhea affects roughly 11%, vomiting about 9%, indigestion 9%, constipation 8%, and reduced appetite around 5%. These symptoms are usually worst during dose increases and tend to improve over time, though some people find them persistent enough to stop treatment.
More serious risks exist but are uncommon. Pancreatitis, an inflammation of the pancreas, is the most closely watched concern. The information leaflet for Mounjaro (tirzepatide’s diabetes version) notes that acute pancreatitis may affect up to 1 in 100 users. Between 2007 and October 2025, the UK’s medicines regulator received 1,296 reports of pancreatitis in people taking GLP-1 or dual GLP-1/GIP drugs, including 19 deaths. Severe cases involving tissue death in the pancreas are described as rare, but regulators have issued updated warnings as prescriptions have surged.
What These Drugs Cost
The list price for Wegovy and Zepbound exceeds $1,000 per month, putting them out of reach for many people without insurance coverage. In practice, the actual cost varies enormously depending on how you access them. Pharmaceutical manufacturers have been selling directly to patients at around $500 per month, and some retail partnerships (including with Costco) offer similar pricing.
Government negotiations have pushed prices lower in some channels. Medicare prices for Wegovy, Zepbound, and their diabetes counterparts are approximately $245 per month, with copays for Medicare enrollees running around $50 per month. A government discount program called TrumpRx brings the cost to roughly $350 per month for eligible buyers. An oral pill version of Wegovy, if and when it becomes widely available, could cost as little as $150 through the manufacturer’s website.
Private insurance coverage remains inconsistent. Many plans cover these medications for diabetes but not for weight loss, and even plans that do cover obesity treatment often require prior authorization and documented medical necessity.
Injectable vs. Oral Options
Until recently, the most effective weight loss drugs were only available as weekly injections using a pen device similar to an insulin pen. Semaglutide is currently the only GLP-1 drug available in both injectable and oral forms, though the two aren’t identical in performance. Real-world data from the Association of British Clinical Diabetologists show that injectable semaglutide produces greater blood sugar reductions than the oral version, while other outcomes are comparable between the two.
A newer oral drug called orforglipron (brand name Foundayo) is also in development. Unlike current GLP-1 drugs, which are peptide-based and fragile in the digestive tract, orforglipron is a small-molecule compound designed specifically to be taken by mouth. If approved, it’s expected to cost around $350 per month, potentially making the class more accessible.
How Long You Stay on Them
These medications are designed as long-term, potentially lifelong treatments. Obesity is treated as a chronic condition, and clinical data consistently show that most people regain a significant portion of lost weight after stopping the drugs. The hunger-reducing effects disappear when the medication leaves your system, which means the biological drive to eat returns to its previous level. This is the aspect that surprises many people: the drugs don’t reset your body’s weight regulation permanently. They manage it for as long as you take them, much like blood pressure medication manages hypertension without curing it.