FDA-approved weight loss pills: phentermine, orlistat, Contrave and Qsymia

Search for diet pills and you get two very different things. FDA-approved medicines were shown in trials to be safe and effective for weight loss, carry a label with warnings, and need a prescription (except low-dose orlistat). Supplements sold as "fat burners" or "natural" pills skip that review: the FDA does not approve dietary supplements before they are sold.

The FDA warns that many diet pills and fat-burning supplements sold online and in stores are likely to contain hidden drug ingredients, can cause serious health problems and hospitalization, and are not guaranteed to work. A product missing from its warning list is not proof that it is safe.

According to the NIDDK (National Institutes of Health) and FDA labels, these are the approved weight-loss medicines:

Until recently, GLP-1 medicines for weight loss came only as shots. In December 2025 the FDA approved the [Wegovy pill](route:guide-semaglutide) (oral semaglutide, once a day), and on April 1, 2026 it approved Foundayo (orforglipron), another once-daily GLP-1 pill. Both are for adults with obesity, or with overweight and at least one weight-related health problem, together with diet and more physical activity.

The practical difference is how you take them. The Wegovy pill is taken in the morning on an empty stomach with a little water, and you wait at least 30 minutes before eating or taking other medicines; Foundayo can be taken any time of day, with or without food. They share warnings with the GLP-1 shots, including the thyroid tumor risk seen in animals and the contraindication if you or your family have a history of medullary thyroid carcinoma or MEN 2.

For the weekly shots, read the guides to Ozempic and Wegovy (semaglutide) and Mounjaro and Zepbound (tirzepatide), or the Ozempic vs. Mounjaro vs. Zepbound vs. Wegovy comparison. The clinic does not offer compounded semaglutide or tirzepatide, which are not FDA-approved; it prescribes only FDA-approved brand medicines.

Phentermine is an appetite suppressant that has been around since 1959 (Adipex-P and generics). Its FDA label limits it to short-term use (a few weeks) as part of a weight-reduction plan, for people with a body mass index (BMI) of 30 or more, or 27 or more with other risk factors such as high blood pressure, diabetes or high cholesterol. It is not recommended for children 16 or younger.

Phentermine is a Schedule IV controlled substance under federal law: it is sold only with a prescription and monitored because it can be misused. It can raise blood pressure and heart rate and cause insomnia, restlessness, dry mouth or constipation. Rarely, it has been linked to pulmonary hypertension and heart valve disease: new shortness of breath, chest pain, fainting or leg swelling means stop it and get care; see also swollen legs.

The label says it should not be used with:

Qsymia pairs a low dose of phentermine with topiramate, a medicine also used for seizures. Unlike phentermine alone, it is approved for long-term use in adults and in teens 12 and older with obesity. Because of the phentermine, it is also a Schedule IV controlled substance.

It can cause birth defects, so it is sold under an FDA safety program (REMS): if you can become pregnant, a negative pregnancy test is recommended before starting and every month, along with effective birth control. It is not used in pregnancy, with glaucoma or hyperthyroidism, or with MAO inhibitors. The highest dose is tapered rather than stopped suddenly, because of the risk of seizures.

Orlistat blocks some of the fat you eat from being absorbed. There are two versions: Xenical, 120 mg by prescription, taken three times a day with each meal that contains fat, and Alli, 60 mg, sold over the counter for overweight adults.

Its most common side effects are bowel changes, mostly in the first weeks: oily spotting, gas with oily discharge, urgent bowel movements and fatty stools. They get worse with high-fat meals.

Because it also blocks fat-soluble vitamins, a multivitamin with vitamins A, D, E, K and beta-carotene is recommended, taken 2 hours before or after orlistat (for example at bedtime). If you take levothyroxine for hypothyroidism, keep the two at least 4 hours apart. It is not used in pregnancy, with chronic malabsorption or with cholestasis.

Contrave combines naltrexone with bupropion, an antidepressant, in extended-release tablets for long-term use in adults. It carries an FDA boxed warning: antidepressants increase the risk of suicidal thoughts and behaviors in children, teens and young adults. It is not approved for anyone under 18.

Its most common side effects are nausea, constipation, headache, vomiting, dizziness, insomnia and dry mouth. It can raise blood pressure and heart rate and increase the risk of seizures.

The label says it is not used with uncontrolled high blood pressure, seizure disorders, anorexia or bulimia, chronic opioid use, other bupropion products, MAO inhibitors in the past 14 days, or while abruptly stopping alcohol, benzodiazepines, barbiturates or seizure medicines.

Saxenda is liraglutide, a GLP-1 medicine injected under the skin every day. It is approved for adults with obesity, or with overweight and a related health problem, and for teens 12 and older who weigh more than 60 kg (about 132 lb) and have obesity.

It shares the GLP-1 warnings: thyroid tumors in animals (a boxed warning), a contraindication if you or your family have a history of medullary thyroid carcinoma or MEN 2, pancreatitis, gallbladder problems, and stomach effects such as nausea, diarrhea, constipation or vomiting. It is not combined with other GLP-1 medicines, and it is stopped if you become pregnant.

Metformin is a type 2 diabetes medicine; the FDA has not approved it for weight loss, though many people search for it for that. In the NIDDK Diabetes Prevention Program, metformin lowered the risk of developing diabetes by 31% compared with placebo in people with prediabetes, and it helped most in people aged 25 to 44, with a BMI of 35 or higher, or with a history of gestational diabetes. For weight, the effect is modest: in the study's long-term follow-up, the metformin group kept an average weight loss of about 2%, compared with 0.2% on placebo, over roughly 10 years.

If you have prediabetes, insulin resistance or PCOS, the doctor evaluates whether metformin or another treatment makes sense for you. For its uses, side effects and vitamin B12, read the metformin guide.

According to the NIDDK and the FDA labels, weight-loss medicines are for adults with a BMI of 30 or more, or 27 or more with a weight-related problem such as high blood pressure, type 2 diabetes or high cholesterol. Some are approved from age 12. On average, people who take a medicine as part of a lifestyle program lose 3% to 12% more of their starting weight over a year than people who do not.

Before recommending a treatment, the doctor reviews your history, your medicines, your blood pressure and your goals. When needed, we give you a lab order online for a lab near you (blood sugar, thyroid, cholesterol, kidney and liver).

If you are losing weight without trying, that is a different problem: read unexplained weight loss, because it needs an evaluation.

If you take a weight-loss medicine and have chest pain, shortness of breath, a pounding heartbeat, severe belly pain that will not go away, yellow skin or eyes, a seizure, or thoughts of harming yourself, go to the emergency room or call 911. For an emotional crisis, call or text 988 or the PAS line at 1-800-981-0023. See when to go to the ER.