There is no single “best” prescription weight loss pill for everyone, but the most effective medications available right now are the newer injectable drugs: tirzepatide (Zepbound) and semaglutide (Wegovy). In a head-to-head clinical trial published in the New England Journal of Medicine, tirzepatide produced 20.2% body weight loss at 72 weeks compared to 13.7% with semaglutide. Both far outperform older oral options, which typically produce 3% to 9% weight loss over a year. The right choice depends on your health profile, what your insurance covers, and how you respond to treatment.
How the Top Medications Compare
Prescription weight loss drugs fall into two broad categories: the newer injectable medications that mimic gut hormones, and older oral pills that work through different mechanisms. The gap in effectiveness between these two groups is significant.
Tirzepatide (Zepbound) currently sits at the top for raw weight loss. It works on two hormone pathways simultaneously, targeting both the appetite signals your gut sends to your brain and the way your body processes blood sugar. In clinical trials, people lost an average of 20.2% of their body weight over about 17 months. For someone weighing 250 pounds, that translates to roughly 50 pounds.
Semaglutide (Wegovy) targets one of those same hormone pathways and delivers an average of 13.7% body weight loss over the same timeframe. That’s still substantial, about 34 pounds for a 250-pound person, and it was considered groundbreaking when it first came to market.
Among the older oral medications, the combination of phentermine and topiramate (Qsymia) performs best. At the highest dose, it produces about 8.9 kilograms (roughly 20 pounds) more weight loss than a placebo over one year, which works out to around 9% of initial body weight. Other oral options lag further behind:
- Naltrexone-bupropion (Contrave): a combination pill that reduces cravings and appetite, producing moderate weight loss
- Orlistat (Xenical, Alli): blocks absorption of about 30% of dietary fat, resulting in roughly 3.4 kilograms (7.5 pounds) more weight loss than placebo over a year
- Phentermine (short-term only): an appetite suppressant approved for a few weeks of use, producing about 3.6 kilograms (8 pounds) beyond placebo
Why the Injectables Work So Well
The newer injectable medications mimic hormones your gut naturally releases after eating. These hormones do several things at once: they signal your brain to feel full, slow down how quickly food leaves your stomach, improve how your body handles blood sugar by boosting insulin and lowering glucagon, and even increase thermogenesis (the calories your body burns generating heat). It’s this multi-pronged approach that explains the dramatic results compared to older drugs that mainly just suppress appetite through a single mechanism.
Tirzepatide’s edge over semaglutide likely comes from targeting two hormone receptors instead of one. By activating both the GLP-1 and GIP pathways, it amplifies the appetite-suppressing and metabolic effects beyond what either signal achieves alone.
Injectable vs. Oral: What to Expect
Both Wegovy and Zepbound are once-weekly injections you give yourself at home using a pen device. You start at a low dose and increase gradually over several months so your body can adjust. Wegovy, for example, starts at 0.25 mg per week and ramps up every four weeks until you reach a maintenance dose of 1.7 mg or 2.4 mg. This slow titration helps reduce side effects, though it also means you won’t see the full effect of the medication for several months.
There is an oral form of semaglutide (Rybelsus), originally approved for type 2 diabetes. Real-world data shows injectable semaglutide produces somewhat greater weight loss than the oral version. At 26 weeks, patients on injectable semaglutide lost 6.24 kilograms on the higher dose compared to 3.70 kilograms with the higher oral dose. The oral pills also need to be taken on an empty stomach with minimal water, which some people find inconvenient.
The older pills like Qsymia and Contrave are taken daily by mouth. For people who strongly prefer avoiding injections, these remain reasonable options, just with more modest results.
Side Effects Across Medications
Gastrointestinal problems are the most common side effects of the injectable medications. About half of people using GLP-1 drugs experience nausea, roughly one-third report diarrhea, and about one in five deal with vomiting. These symptoms tend to be worst during dose increases and often improve as your body adjusts. The gradual titration schedule exists specifically to minimize this.
The older medications carry their own side effect profiles. Orlistat can cause oily stools, gas, and urgent bowel movements, particularly after high-fat meals, because it’s literally blocking fat absorption. Phentermine can raise heart rate and blood pressure and cause insomnia, which is part of why it’s only approved for short-term use. The phentermine-topiramate combination carries a risk of tingling in the hands and feet, dry mouth, and constipation. Contrave can cause nausea and headaches and carries a boxed warning about suicidal thoughts, though this is related to the bupropion component.
Who Qualifies for These Medications
Prescription weight loss medications are generally available if you have a BMI of 30 or greater, or a BMI of 27 or greater with at least one weight-related health condition like high blood pressure or type 2 diabetes. Your doctor will also consider your medical history, since certain conditions rule out specific drugs. Phentermine-containing medications aren’t appropriate for people with uncontrolled hypertension, for example, and the injectables aren’t recommended for people with a personal or family history of a rare type of thyroid cancer.
Cost and Insurance Coverage
Cost has been the biggest barrier to the injectable medications. Wegovy has carried a list price around $1,350 per month, while Zepbound has been about $1,086 per month. Many insurance plans have excluded weight loss drugs from coverage, leaving patients to pay out of pocket.
That landscape is shifting. Under a recently announced federal pricing program, the monthly cost of Wegovy and Zepbound is set to drop to roughly $350 for participants, with Medicare pricing at $245 per month and a co-pay of just $50 for Medicare beneficiaries. Medicare will also cover these drugs for patients with obesity and related conditions for the first time. State Medicaid programs will have access to the same pricing. If an oral version of Wegovy receives FDA approval, initial pricing through the program would be $150 per month.
The older oral medications are significantly cheaper. Generic phentermine costs as little as $15 to $30 per month, and generic orlistat (Alli) is available over the counter. Qsymia and Contrave typically run $150 to $300 per month without insurance but have more established generic pathways.
Choosing the Right Option
If maximum weight loss is the priority and cost or insurance coverage isn’t a barrier, tirzepatide (Zepbound) has the strongest clinical data. Semaglutide (Wegovy) is a close second and may be a better fit depending on your insurance formulary or how you tolerate each drug. Some people who experience significant nausea on one do better switching to the other.
If injectables aren’t accessible or you prefer pills, phentermine-topiramate (Qsymia) offers the best weight loss among oral options. For people who need a long-term oral medication without stimulant properties, naltrexone-bupropion (Contrave) or orlistat may be appropriate, though expectations should be calibrated to their more modest results of 3% to 5% body weight loss.
All of these medications work best alongside changes in eating habits and physical activity. Clinical trials for every weight loss drug are conducted with lifestyle counseling included, and the results reflect that combination. Weight regain after stopping medication is common across all categories, which is why many people stay on these drugs long-term.