Several prescription pills can produce meaningful weight loss, and the most effective ones available today can help people lose 15% or more of their body weight. Six medications are FDA-approved for long-term weight management, while a handful of others are approved for short-term use. Over-the-counter supplements, by contrast, have little reliable evidence behind them.
Which pill makes sense depends on your starting weight, health history, and how your body responds. Here’s what each option actually does and what kind of results to expect.
GLP-1 and Dual-Action Injectables
The most talked-about weight loss medications right now are semaglutide (Wegovy) and tirzepatide (Zepbound). These aren’t traditional pills. They’re weekly injections, though oral versions are in development. They work by mimicking a gut hormone called GLP-1 that signals your brain to reduce appetite and slow digestion, so you feel full faster and stay satisfied longer. Tirzepatide goes a step further by mimicking a second hormone (GIP), which may explain why it tends to produce even greater weight loss.
In clinical trials, tirzepatide helped people lose between 15% and nearly 21% of their body weight over 72 weeks. For someone who weighs 250 pounds, that’s roughly 38 to 52 pounds. Semaglutide typically produces slightly less weight loss but remains one of the most effective options available. An older injectable in this class, liraglutide (Saxenda), works through the same GLP-1 pathway but requires daily injections and generally produces more modest results.
The most common side effects are gastrointestinal: nausea, vomiting, diarrhea, and constipation, especially during the first few weeks as your dose increases. Less common but serious risks include pancreatitis, gallstone attacks, and gastroparesis (where the stomach empties too slowly). These medications are approved for adults, and semaglutide and liraglutide are also approved for children 12 and older.
Prescription Pills You Take by Mouth
If you’re specifically looking for a pill rather than an injection, three FDA-approved oral medications are available for long-term use.
Phentermine-topiramate (Qsymia) combines two older drugs into one capsule. Phentermine suppresses appetite, while topiramate (originally a seizure medication) makes you feel full sooner. It’s one of the more effective oral options. Common side effects include dry mouth, tingling in the hands and feet, constipation, and trouble sleeping. It’s approved for adults and children 12 and older.
Naltrexone-bupropion (Contrave) pairs a drug used for addiction treatment with an antidepressant. Together, they act on brain pathways involved in hunger and cravings. This pill can be particularly helpful for people who struggle with emotional eating or food cravings rather than pure hunger. Side effects often include nausea, headache, and constipation. It carries a boxed warning about suicidal thoughts, inherited from bupropion’s antidepressant class. It’s approved for adults only.
Orlistat (Xenical) works completely differently from the others. Instead of targeting your brain, it blocks about 30% of the fat you eat from being absorbed in your gut. That unabsorbed fat passes through your digestive system, which is why the most notable side effects are oily stools, gas, and urgent bowel movements, particularly after high-fat meals. Weight loss tends to be more modest compared to the newer medications. A lower-dose version (Alli) is available over the counter.
Short-Term Stimulant Pills
Phentermine on its own (without topiramate) is one of the most commonly prescribed weight loss medications. It works as an appetite suppressant similar to amphetamines. The catch is that it’s only recommended for short-term use, typically less than 12 weeks. Concerns about cardiovascular risk and potential for dependence have kept it from gaining approval for longer treatment. Other short-term stimulant options exist, but they carry similar limitations. These pills are often used as a jumpstart while someone builds new eating and exercise habits.
What Happens in the First Few Months
Weight loss medications don’t work overnight. During the first month, most people notice reduced hunger, smaller portion sizes, and fewer cravings. Actual scale changes tend to be modest early on because doses are typically started low and increased gradually to minimize side effects.
By month two, weight loss becomes more visible. Clothes fit differently, and weekly progress feels more consistent. Month three is when results start to feel significant for most people, with noticeable fat loss, more natural-feeling food choices, and improved energy. Clinical trials measure results at longer intervals, and peak weight loss for most medications occurs somewhere between 6 and 18 months of continuous use.
One important reality: if you stop taking these medications, weight typically returns. Most of the current evidence suggests that weight loss drugs work best as ongoing treatment rather than a short course.
Who Qualifies for a Prescription
Weight loss medications are generally prescribed for adults with a BMI of 30 or higher, which the WHO defines as the threshold for obesity. People with a BMI of 27 or higher may also qualify if they have a weight-related health condition like type 2 diabetes, high blood pressure, or high cholesterol. Your doctor will evaluate your full medical history, since some of these medications are off-limits for people with certain heart conditions, uncontrolled blood pressure, or a history of eating disorders.
Over-the-Counter Supplements
The supplement aisle is full of products claiming to burn fat, boost metabolism, or block carbs. The evidence for nearly all of them is weak. A comprehensive review by the National Institutes of Health concluded that the evidence supporting dietary supplements for weight loss is “inconclusive and unconvincing,” and that little is known about whether they’re effective while some carry potential for harm.
Green tea extract is one of the more studied options. A review of 14 clinical trials found it reduced body weight by less than 1 kilogram (about 2 pounds) more than a placebo. When researchers looked only at well-designed studies conducted outside Japan, the difference disappeared entirely. There’s also growing evidence that green tea extract can cause liver damage. Garcinia cambogia showed similarly tiny effects, about 0.88 kilograms over 2 to 12 weeks, and even that result fell apart in the most rigorous trials. Conjugated linoleic acid (CLA) reduces body fat in animal studies but produces effects in humans that are too small to matter in practice.
The one exception in the OTC space is low-dose orlistat (Alli), which is a genuine pharmaceutical available without a prescription. It blocks fat absorption the same way its prescription-strength version does, just at a lower dose.
Comparing Your Options
- Most effective overall: Tirzepatide (Zepbound) and semaglutide (Wegovy) produce the greatest weight loss but require injections and tend to be expensive.
- Best oral prescription option: Phentermine-topiramate (Qsymia) is the strongest pill-form medication for long-term use.
- Best for emotional or craving-driven eating: Naltrexone-bupropion (Contrave) targets the reward and craving circuits in the brain.
- Only OTC option with real evidence: Orlistat (Alli) works, but produces modest results and comes with digestive side effects.
- Supplements: No over-the-counter supplement has shown clinically meaningful weight loss in high-quality human trials.
Cost and insurance coverage vary widely. GLP-1 medications can run over $1,000 per month without insurance, while older medications like phentermine and orlistat are available as affordable generics. Checking your specific insurance formulary is the fastest way to narrow down which options are realistic for you.