Your doctor can prescribe from six FDA-approved medications for long-term weight management, ranging from daily pills to weekly injections. Which one you qualify for depends on your body mass index (BMI), your health history, and how your body responds to treatment. The options have expanded significantly in recent years, and the newest injectable medications produce dramatically more weight loss than anything available a decade ago.
Who Qualifies for Prescription Weight Loss Medication
The standard threshold is a BMI of 30 or higher. If your BMI is 27 or higher and you have at least one weight-related health condition, such as high blood pressure, type 2 diabetes, or high cholesterol, you also qualify. These are the same criteria used across all the FDA-approved options. Your doctor will typically recommend medication alongside changes to diet and physical activity, not as a standalone fix.
Weekly Injections: The Most Effective Options
The two medications producing the largest weight loss results are both weekly injections you give yourself at home using a pen device, similar to an insulin pen.
Semaglutide (sold as Wegovy) works by mimicking a gut hormone called GLP-1 that regulates appetite and slows digestion. In clinical trials, people taking semaglutide lost an average of 14.9% of their body weight over about 16 months. For someone weighing 250 pounds, that translates to roughly 37 pounds.
Tirzepatide (sold as Zepbound) targets two gut hormones instead of one, and the results reflect that. In its main clinical trial, people lost between 15% and 20.9% of their body weight over 72 weeks, depending on the dose. At the highest dose, someone starting at 250 pounds could expect to lose around 52 pounds on average. Tirzepatide is currently the most effective weight loss medication on the market.
Both medications are injected once per week and are gradually increased over several weeks to help your body adjust. Neither is currently on the FDA’s drug shortage list, which means supply has stabilized after earlier availability problems.
Common Side Effects of Injectable Medications
Nausea is the most frequent side effect of both semaglutide and tirzepatide, along with vomiting, diarrhea, and loss of appetite. These symptoms tend to be worst when you first start the medication or when your dose increases, and they usually improve over time.
Rare but serious risks include pancreatitis, kidney injury, and a possible link to a type of thyroid cancer called medullary thyroid carcinoma. People with a personal or family history of that specific cancer should not take these medications. Your doctor will review your history before prescribing.
Daily Injection: Liraglutide
Liraglutide (sold as Saxenda) is an older GLP-1 medication that requires a daily injection rather than a weekly one. It works through the same basic mechanism as semaglutide but produces less weight loss. It remains an option for people who don’t respond well to or can’t access the newer weekly injectables, and it’s approved for adolescents aged 12 and older.
Oral Medications You Take as a Pill
If you prefer not to inject, three FDA-approved pills are available for long-term use.
Phentermine-topiramate (Qsymia) is taken once daily. It combines a stimulant that suppresses appetite with a medication originally used for seizures and migraines that also reduces hunger. Of the oral options, this combination generally produces the most weight loss. It’s approved for adults and adolescents aged 12 and older.
Naltrexone-bupropion (Contrave) targets both the appetite center in the brain and the reward system that drives cravings. It combines a medication used for addiction treatment with one used for depression. The dose is gradually increased over four weeks, starting with one pill in the morning and building to two pills twice daily. This slow ramp-up helps minimize side effects like nausea and headache.
Orlistat (Xenical) works differently from everything else on this list. Instead of acting on your brain or hormones, it blocks your body from absorbing about a third of the fat you eat. You take it three times a day with meals. The weight loss is more modest, but it’s the only option available in a lower-dose, over-the-counter version (sold as Alli). The main downside: eating high-fat meals while taking orlistat causes oily stools, gas, and urgent bowel movements, which is unpleasant but also acts as a built-in motivator to eat less fat.
Short-Term Prescriptions
Phentermine (sold as Adipex-P) is FDA-approved only for short-term use, defined as a few weeks. It’s a stimulant that suppresses appetite and has been around for decades. Your doctor may prescribe it as a jumpstart while you build new eating and exercise habits, but it’s not meant to be taken indefinitely. It carries the same BMI requirements: 30 or higher, or 27 with a weight-related health condition.
Off-Label Options Your Doctor Might Mention
Metformin, a medication primarily used for type 2 diabetes and prediabetes, is sometimes prescribed off-label for weight loss. The evidence behind it is modest. The largest study, the Diabetes Prevention Program, found that people taking metformin lost about 2.1 kilograms (roughly 4.6 pounds) on average, with more adherent patients losing around 3.5% of their body weight. Smaller studies in people without diabetes generally haven’t found significant weight loss.
The FDA has not approved metformin as a weight loss drug. Medical guidelines recommend it mainly for people who also have prediabetes or insulin resistance that hasn’t responded to other approaches. If your doctor suggests it, it’s likely because they’re treating a metabolic issue alongside your weight, not because it’s a strong weight loss tool on its own.
How to Talk to Your Doctor About Options
The right medication depends on several personal factors: your BMI, any existing health conditions, whether you’re comfortable with injections, your insurance coverage, and your budget. The newer injectables produce the most dramatic results, but they’re also the most expensive without insurance, often running over $1,000 per month at retail price. The oral medications and phentermine cost significantly less.
Your doctor will likely want to discuss what you’ve already tried. Most prescribers expect that you’ve made some effort with diet and exercise before turning to medication. That said, the medical community increasingly recognizes obesity as a chronic condition that responds to pharmacological treatment, not a personal failing that willpower alone should solve.
It’s also worth knowing that weight tends to return if you stop taking these medications. Studies on semaglutide and tirzepatide show that most people regain a significant portion of lost weight after discontinuation. This means your doctor may recommend staying on medication long-term, which makes insurance coverage and affordability an important part of the conversation from the start.