Several FDA-approved medications can produce meaningful weight loss, ranging from about 5% to over 20% of body weight depending on the drug. The most effective options available right now are injectable medications that mimic gut hormones, but oral pills also work for many people. Which one fits you depends on your starting weight, health conditions, insurance coverage, and how you tolerate side effects.
To qualify for a prescription weight loss drug, you generally need a BMI of 30 or higher, or a BMI of 27 or higher with at least one weight-related health condition like type 2 diabetes, high blood pressure, high cholesterol, sleep apnea, or heart disease.
Injectable GLP-1 and Dual Agonist Medications
The most powerful weight loss drugs currently available are weekly injections that mimic hormones your gut naturally releases after eating. These hormones slow stomach emptying, reduce appetite, and act on brain areas that control hunger and fullness. Two medications dominate this category.
Semaglutide (sold as Wegovy for weight loss) was the first to gain widespread attention. It targets a single gut hormone receptor called GLP-1. In clinical trials, participants lost roughly 15% of their body weight over about 16 months. That translates to around 35 pounds for someone starting at 230.
Tirzepatide (sold as Zepbound) targets two hormone receptors instead of one, adding GIP to the GLP-1 pathway. This dual action produces even greater weight loss. In clinical trials, the highest dose led to a 20.9% reduction in body weight, an average of 48 pounds lost. Even the lowest dose produced a 15% loss, about 34 pounds. These results far exceed anything oral medications have achieved.
Both drugs are given as a weekly self-injection using a pen device, similar to an insulin pen. You start at a low dose and gradually increase over several months to let your body adjust and minimize side effects.
Side Effects of Injectable Medications
Nausea is the most common complaint, affecting roughly 22% of people on semaglutide and 25% on tirzepatide. Vomiting occurs in about 9% of users for both drugs. One notable difference: constipation affects about 8% of semaglutide users but is rare with tirzepatide. These side effects are usually worst during the dose-increase phase and tend to improve over time. Most people find them manageable, though a small percentage stop treatment because of persistent stomach issues.
Oral Prescription Options
Not everyone wants or qualifies for injections, and several pill-based medications offer a less dramatic but still meaningful alternative.
The combination of phentermine and topiramate (sold as Qsymia) is the most effective oral option. Phentermine triggers the release of brain chemicals that suppress appetite, while topiramate enhances feelings of fullness through a separate mechanism. Together, they produced about 10% body weight loss at the highest dose in clinical trials, compared to roughly 1.5% with a placebo. That’s about half the effect of the injectable drugs, but still enough to improve blood pressure, blood sugar, and cholesterol in many people.
Bupropion and naltrexone (sold as Contrave) works through a different approach entirely. Rather than mimicking gut hormones, it targets the brain’s appetite center and reward system simultaneously. Bupropion increases the activity of brain circuits that regulate hunger, while naltrexone blocks opioid receptors that would normally dampen that effect. The combination produced about 5.4% weight loss over 56 weeks in clinical trials. When paired with an intensive lifestyle program including diet coaching and exercise, results improved to about 8%. This medication can be particularly useful for people whose eating is driven more by cravings and reward-seeking than by physical hunger.
Over-the-Counter: Orlistat
Orlistat is the only FDA-approved weight loss drug available without a prescription (at a lower dose, sold as Alli). It works completely differently from every other option on this list. Instead of affecting your brain or hormones, it blocks enzymes in your gut that break down fat. At prescription strength, it prevents about 30% of the fat you eat from being absorbed. That unabsorbed fat passes through your digestive system, which means the calories it contains never enter your body.
The tradeoff is that unabsorbed fat has to go somewhere. Oily stools, gas, and urgent bowel movements are common, especially after high-fat meals. Weight loss with orlistat is modest, typically 5 to 7% of body weight. Many people find the gastrointestinal side effects motivate them to eat less fat, which contributes to the weight loss effect. It’s best suited for people who want a non-systemic option that doesn’t affect brain chemistry.
What Happens When You Stop
One of the most important things to understand about weight loss medications is that they work for as long as you take them. Your body treats the medicated state as temporary. When you stop a GLP-1 or dual agonist drug, appetite returns, metabolic changes reverse, and most people regain a significant portion of the weight they lost, often within a year. This pattern holds across all classes of weight loss drugs, not just injectables.
This doesn’t mean the medications are a failure. It means obesity is a chronic condition, similar to high blood pressure or diabetes, where ongoing treatment maintains the benefit. Some people use medication to lose weight and then transition to a lower maintenance dose. Others stop and accept some regain while trying to hold onto a portion of the loss through diet and exercise changes they built during treatment. The key is going in with realistic expectations: these drugs are powerful tools, but they’re not one-time fixes.
Cost and Access
Cost remains the biggest barrier for most people. The injectable medications are expensive without insurance. Wegovy’s self-pay price starts at $199 per month for the pen injector, with higher doses running $349 to $399 monthly. Zepbound falls in a similar range. With commercial insurance that covers the drug, copays can drop significantly, sometimes to as little as $25 per month for Wegovy. But many insurance plans still don’t cover weight loss medications, or they require prior authorization with documentation of failed diet attempts.
If your insurance doesn’t cover a specific drug, your doctor can submit an appeal or request that your employer add coverage. The oral medications tend to be cheaper, and generic phentermine (available on its own for short-term use) is inexpensive. Orlistat’s over-the-counter version costs roughly $40 to $60 per month.
What’s Coming Next
The next frontier is a class of drugs called triple agonists, which activate three hormone receptors instead of one or two. Retatrutide, the furthest along in development, targets GLP-1, GIP, and glucagon receptors simultaneously. In a Phase 3 trial involving people with type 2 diabetes, the highest dose produced 16.8% body weight loss over just 40 weeks. Trials in people without diabetes are expected to show even larger effects, since diabetes tends to make weight loss harder. Retatrutide is not yet FDA-approved, but it represents where the field is heading: increasingly effective drugs that push weight loss closer to what surgery can achieve.