Doctors can prescribe several FDA-approved medications for weight loss, ranging from daily pills to weekly injections. The most effective options currently available are injectable GLP-1 drugs like semaglutide (Wegovy) and tirzepatide (Zepbound), which produce average weight loss of 15% to 21% of body weight over about 16 months. But these aren’t the only choices. There are also oral medications, fat-blocking drugs, and off-label options your doctor may consider depending on your health profile and budget.
Who Qualifies for a Prescription
Weight loss medications are generally prescribed for adults with a BMI of 30 or higher (classified as obesity). You may also qualify with a BMI of 27 or higher if you have at least one weight-related health condition, such as type 2 diabetes, high blood pressure, or high cholesterol. Your doctor will typically recommend these medications alongside changes to diet and physical activity, not as a replacement for them.
GLP-1 Injectable Medications
The biggest shift in weight loss treatment over the past few years has been the rise of GLP-1 receptor agonists. These are weekly injections that mimic a gut hormone involved in appetite regulation. They work by signaling to areas of the brain that control hunger and fullness, making you feel satisfied with less food. Two are currently approved specifically for weight management.
Semaglutide (Wegovy) produced an average weight loss of 14.9% of body weight over 68 weeks in its landmark clinical trial. That means someone starting at 250 pounds could expect to lose roughly 37 pounds on average. The dose is gradually increased over the first several months to reduce side effects.
Tirzepatide (Zepbound) works similarly but mimics two gut hormones instead of one. In clinical trials, participants lost between 15% and 20.9% of their body weight over 72 weeks, depending on the dose. At the highest dose, that translates to about one-fifth of total body weight lost.
Liraglutide (Saxenda) is an older GLP-1 option that requires daily injections rather than weekly. It generally produces less weight loss than semaglutide or tirzepatide but remains available for people who don’t tolerate the newer drugs.
Oral Prescription Options
Not everyone wants or can use injections. Several pill-form medications are FDA-approved for weight loss, though they tend to produce more modest results.
Phentermine-topiramate (Qsymia) combines two ingredients: one that suppresses appetite and another originally developed for seizures and migraines that also appears to reduce hunger and increase feelings of fullness. Of the oral options, this combination tends to produce the most weight loss.
Naltrexone-bupropion (Contrave) pairs two medications that individually treat addiction and depression. Together, they act on brain pathways involved in cravings and reward-driven eating. This can be a particularly useful option for people whose weight is tied to compulsive or emotional eating patterns.
Orlistat (Xenical) takes a completely different approach. Instead of acting on the brain, it blocks about 30% of the fat you eat from being absorbed in your gut. The unabsorbed fat passes through your digestive system, which means the drug works best on higher-fat diets but also comes with uncomfortable digestive side effects like oily stools and gas. A lower-dose version (Alli) is available over the counter. Orlistat typically produces more modest weight loss than the other options, averaging around 5 to 7 additional pounds compared to diet alone.
Off-Label Medications
Doctors sometimes prescribe medications off-label for weight loss, meaning the drug is FDA-approved for a different condition but has shown weight loss as a benefit. Two of the most common are metformin and topiramate used individually.
Metformin, a diabetes medication, appears to promote modest weight loss partly by increasing the body’s own production of GLP-1, the same hormone that the injectable drugs mimic. Topiramate, a seizure and migraine drug, suppresses appetite through its effects on brain signaling. Both are relatively inexpensive compared to newer brand-name options, which makes them appealing when cost is a barrier. However, the weight loss they produce is generally less dramatic than what you’d see with FDA-approved weight loss medications.
Phentermine alone (without topiramate) is also commonly prescribed as a short-term appetite suppressant, typically for 12 weeks or less.
Common Side Effects
The side effect profile varies by drug class, but there are clear patterns.
GLP-1 medications (Wegovy, Zepbound, Saxenda) share a set of gastrointestinal side effects: nausea, vomiting, diarrhea, and constipation. These are the most common complaints by a wide margin and tend to be worst during the dose-escalation period in the first few months. For most people, they ease over time. Less common but more serious risks include pancreatitis (inflammation of the pancreas), gastroparesis (severely slowed stomach emptying), bowel obstruction, and gallstone attacks.
Orlistat’s side effects are almost entirely digestive, tied directly to the unabsorbed fat passing through your system. Diarrhea, oily spotting, and gas are frequent complaints, especially after high-fat meals.
The oral appetite-suppressing combinations (Qsymia, Contrave) can cause dry mouth, insomnia, constipation, and tingling sensations. Qsymia carries specific warnings for women of childbearing age because topiramate can cause birth defects.
Who Should Avoid Certain Medications
GLP-1 drugs are not appropriate for everyone. People with a personal or family history of a type of thyroid cancer called medullary thyroid carcinoma should avoid them. Those with a history of pancreatitis or active pancreatic conditions are also generally steered away from GLP-1 medications because the drugs carry some pancreatitis risk. If you’re undergoing cancer treatment with nausea and vomiting as side effects, GLP-1 drugs can make those symptoms worse and may also contribute to muscle loss that interferes with your ability to tolerate treatment.
Phentermine-based medications are stimulants and should be avoided by people with uncontrolled high blood pressure, heart disease, or hyperthyroidism. They also carry a risk of dependence with long-term use, which is why phentermine alone is typically prescribed for short periods.
Cost and Insurance Coverage
Cost has been the single biggest barrier to the newer weight loss drugs. The list prices for Wegovy and Zepbound have hovered around $1,000 to $1,350 per month. Many private insurers have been slow to cover them, and Medicare historically did not cover weight loss medications at all.
That landscape is shifting. Recent pricing agreements have brought costs down to around $350 per month for some purchasers, and Medicare coverage for obesity medications is expanding. Medicare beneficiaries may pay a copay of roughly $50 per month under newer coverage arrangements. Still, your actual out-of-pocket cost will depend heavily on your specific insurance plan. It’s worth calling your insurer directly before assuming coverage.
The older oral medications are significantly cheaper. Generic orlistat, metformin, and topiramate can cost under $30 per month at many pharmacies, making them practical alternatives when the newer drugs aren’t financially accessible.
How Long You’ll Take Them
Most weight loss medications are intended for long-term, potentially indefinite use. Obesity is treated as a chronic condition, and research consistently shows that stopping medication leads to weight regain. In clinical trials of GLP-1 drugs, participants who stopped treatment regained a significant portion of their lost weight within a year. This means that for most people, the decision to start a weight loss medication is a commitment to staying on it as long as it’s working and tolerable.
The exception is phentermine alone, which is approved only for short-term use of up to 12 weeks. Your doctor may also set specific benchmarks. If you haven’t lost a meaningful amount of weight (typically 5% of body weight) after three to six months on a given medication, they’ll likely suggest switching to a different option rather than continuing.
What’s in the Pipeline
The next generation of weight loss drugs is already in late-stage clinical trials. Retatrutide, developed by Eli Lilly, mimics three gut hormones instead of two. In a recent Phase 3 trial, participants on the highest dose lost an average of 28.7% of their body weight, roughly 71 pounds, over 68 weeks. That’s substantially more than any currently available medication. Gastrointestinal side effects remained common, with nausea affecting about 43% of participants at the higher dose and roughly 18% to 19% discontinuing due to side effects. If approved, retatrutide and similar drugs could push average weight loss outcomes closer to what’s currently achievable only with bariatric surgery.