Prescription Weight Loss Drugs: A Guide to FDA-Approved Options

The best prescription weight loss drug depends on your health profile, but in clinical trials tirzepatide (Zepbound) produces the largest average weight loss — about 20.9% of body weight over 72 weeks — followed by semaglutide (Wegovy) at ~15% [1][2]. The U.S. Food and Drug Administration (FDA) has approved seven medications for long-term weight management: three injectable GLP-1-based drugs and four older oral options. The right choice balances effectiveness, side effects, cost, and what you can access.

What are prescription weight loss medications?

Prescription weight loss drugs — also called anti-obesity medications (AOMs) — are FDA-approved to help people lose weight and keep it off when used with a reduced-calorie diet and more physical activity [3]. Obesity is a chronic disease, not a willpower problem. Major medical bodies, including the American Medical Association and the World Health Organization, classify it that way and recommend long-term treatment, similar to how high blood pressure or diabetes is managed [4].

The seven FDA-approved options fall into a few categories based on how they work:

• GLP-1 and GIP/GLP-1 receptor agonists (injectables): semaglutide, tirzepatide, liraglutide.
• Combination appetite-and-craving medications (oral): phentermine-topiramate, naltrexone-bupropion.
• Stimulant appetite suppressants (oral, short-term): phentermine.
• Fat absorption inhibitors (oral): orlistat.

For a deeper look at the GLP-1 class specifically, see our overview of GLP-1 medications.

Who qualifies for prescription weight loss drugs?

BMI and comorbidity criteria

Eligibility is based on body mass index (BMI) and whether you have a weight-related health condition. The FDA generally approves anti-obesity medications for adults who have [3][5]:

• A BMI of 30 or higher (obesity), or
• A BMI of 27 or higher (overweight) with at least one weight-related condition — for example, type 2 diabetes, high blood pressure, high cholesterol, obstructive sleep apnea, or cardiovascular disease.

Some medications are also approved for adolescents. Semaglutide (Wegovy), liraglutide (Saxenda), and phentermine-topiramate (Qsymia) are approved for use in children aged 12 and older who meet specific criteria [6][7][8]. Our guide on BMI and obesity treatment walks through how clinicians read these thresholds in context.

When lifestyle changes aren't enough

Guidelines from the Endocrine Society and the American Gastroenterological Association recommend considering medication when diet and exercise alone haven't produced enough weight loss to improve health — typically defined as at least 5% of body weight [5][9]. Medication is not a failure of willpower; obesity involves hormones, brain signaling, and metabolism that lifestyle changes alone often cannot override [4].

How do prescription weight loss drugs work?

GLP-1 and GIP/GLP-1 receptor agonists

Glucagon-like peptide-1 (GLP-1) is a hormone your gut releases after meals. It tells your brain you're full, slows gastric emptying (how fast food leaves the stomach), and helps the pancreas release insulin [10]. GLP-1 receptor agonists are medications that mimic this hormone, so you feel fuller, eat less, and have fewer food cravings [1][10].

Tirzepatide goes one step further — it activates both the GLP-1 receptor and the GIP (glucose-dependent insulinotropic polypeptide) receptor, another gut hormone involved in appetite and how the body handles fat and sugar. This dual action appears to produce greater weight loss than GLP-1 alone [1].

Appetite suppressants

Phentermine is a stimulant that acts on the brain to reduce hunger. It is chemically related to amphetamines but less potent, and it is approved only for short-term use (usually up to 12 weeks) [11].

Fat absorption inhibitors

Orlistat blocks an enzyme called pancreatic lipase, which the gut uses to break down dietary fat. About 25–30% of the fat you eat passes through undigested instead of being absorbed as calories [12].

Combination medications

Two oral medications combine drugs that target appetite and cravings through different pathways:

• Phentermine-topiramate (Qsymia) pairs an appetite suppressant with an anti-seizure drug that reduces appetite and increases feelings of fullness [13].
• Naltrexone-bupropion (Contrave) combines a medication used for addiction (naltrexone) with an antidepressant (bupropion) to reduce hunger and food cravings via brain reward pathways [14].

What are the FDA-approved prescription weight loss drugs?

Semaglutide (Wegovy)

Semaglutide is a once-weekly injection. Under the brand name Wegovy, it is FDA-approved for chronic weight management in adults and adolescents 12 and older, and for reducing the risk of major cardiovascular events (heart attack, stroke, cardiovascular death) in adults with established heart disease and overweight or obesity [6][15]. The same molecule is sold as Ozempic for type 2 diabetes [16]. Semaglutide (a GLP-1 receptor agonist) is also available as a compounded formulation through licensed 503A pharmacies in certain situations. For specific tolerability information, see our notes on semaglutide side effects.

Tirzepatide (Zepbound)

Tirzepatide is a once-weekly injection that activates both GIP and GLP-1 receptors. It is approved as Zepbound for chronic weight management and for moderate-to-severe obstructive sleep apnea in adults with obesity [17]. The same molecule is sold as Mounjaro for type 2 diabetes [18]. Tirzepatide (a dual GIP/GLP-1 receptor agonist) is also available as a compounded formulation through licensed 503A pharmacies in certain situations. Our tirzepatide dosing guide walks through the typical titration schedule clinicians use. For a head-to-head, see Wegovy vs Zepbound.

Liraglutide (Saxenda)

Liraglutide is a daily GLP-1 injection. Approved as Saxenda for adults and adolescents 12 and older, it was the first GLP-1 cleared for weight management [7]. Daily dosing makes it less convenient than the weekly options, but it remains a valid choice.

Phentermine-topiramate (Qsymia)

Qsymia is a once-daily capsule taken in the morning. It is approved for adults and adolescents 12 and older [8]. Because topiramate can cause birth defects, women of childbearing age must have a negative pregnancy test before starting and monthly during treatment [13].

Naltrexone-bupropion (Contrave)

Contrave is an oral tablet taken twice daily after a gradual dose-up over four weeks. It carries a boxed warning about suicidal thoughts and behaviors (from the bupropion component) and is not for people with uncontrolled high blood pressure, seizure disorders, or those using opioids [14].

Orlistat (Xenical)

Orlistat is taken with each fat-containing meal — up to three times a day. It is the only weight-loss drug approved for over-the-counter use at a lower dose (sold as Alli). Side effects related to undigested fat (oily stools, urgency, gas) are common and often limit use [12].

Phentermine (Adipex-P)

Phentermine alone is approved only for short-term use (up to 12 weeks) as part of a weight-loss program. It is a controlled substance because of its stimulant properties and potential for dependence [11].

How much weight can you lose on each medication?

The table below shows average weight loss from the key registration trials. Individual results vary, and these numbers reflect trial conditions (regular check-ins, lifestyle counseling, and the highest tolerated dose). Real-world results may be lower.

What are the side effects of prescription weight loss drugs?

Common side effects

Most side effects are dose-related and tend to improve over time. Highlights from each class:

• GLP-1 / GIP–GLP-1 (semaglutide, tirzepatide, liraglutide): nausea, vomiting, diarrhea, constipation, indigestion, and fatigue, especially during dose increases [6][7][17].
• Phentermine-topiramate: tingling in hands and feet, dry mouth, constipation, altered taste, insomnia [13].
• Naltrexone-bupropion: nausea, headache, constipation, insomnia, dizziness [14].
• Orlistat: oily stools, urgent bowel movements, gas with discharge — usually triggered by high-fat meals [12].
• Phentermine: increased heart rate, elevated blood pressure, insomnia, dry mouth, restlessness [11].

Serious risks and contraindications

• GLP-1 medications carry a boxed warning about thyroid C-cell tumors based on rodent studies. They should not be used by people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2 (MEN 2) [6][17].
• GLP-1s have been associated with pancreatitis, gallbladder disease, and (rarely) bowel obstruction [6][17].
• Phentermine and phentermine-topiramate are not recommended for people with uncontrolled high blood pressure, heart disease, hyperthyroidism, or glaucoma; both can increase heart rate [11][13].
• Topiramate (in Qsymia) can cause serious birth defects; effective contraception is required [13].
• Naltrexone-bupropion has a boxed warning for suicidal thoughts and behaviors and is contraindicated in seizure disorders, uncontrolled hypertension, and current opioid use [14].
• Orlistat can reduce absorption of fat-soluble vitamins (A, D, E, K); a daily multivitamin is recommended [12].

How much do prescription weight loss medications cost?

Branded GLP-1s like Wegovy and Zepbound carry list prices over $1,000 per month before insurance or manufacturer savings programs [22]. Coverage for anti-obesity medications varies widely — our overview of insurance coverage for weight loss drugs goes deeper:

• Medicare currently does not cover medications used solely for weight loss, though it may cover the same drugs prescribed for diabetes or, in some cases, cardiovascular risk reduction [23].
• Commercial insurance plans differ — some cover GLP-1s for obesity with prior authorization; many do not.
• Older medications (phentermine, orlistat, generic naltrexone-bupropion components) are far less expensive — often $20–$100 per month.

Compounded versions of semaglutide and tirzepatide have been available through licensed 503A compounding pharmacies during FDA-declared shortages, often at lower out-of-pocket prices [24]. A 503A pharmacy is a state-licensed pharmacy that prepares medications for individual patients based on a prescription. Availability and rules change as shortage status changes, so confirm current FDA status with your clinician before assuming compounded options are available for you. Chia is one of several licensed telehealth providers that can evaluate whether a compounded option is appropriate for an individual patient.

How long do you take prescription weight loss medication?

Most anti-obesity medications are intended for long-term use, because obesity is a chronic condition. The STEP 4 trial showed that people who stopped semaglutide after 20 weeks regained about two-thirds of the weight they had lost within a year [25]. The SURMOUNT-4 trial showed a similar pattern with tirzepatide [26]. Phentermine alone is an exception — it is FDA-approved only for short-term use (typically up to 12 weeks) [11].

In practice, ongoing use means working with a clinician on the lowest effective dose, monitoring side effects, and pairing the medication with sustainable nutrition and activity habits [5].

How do you get a prescription for weight loss medication?

Prescription weight loss medications require a clinical evaluation. A clinician will review your BMI, weight-related health conditions, current medications, mental health history, and prior weight loss attempts to decide if a prescription is appropriate — and which one fits your situation best. Our walkthrough on how to get a GLP-1 prescription has more detail on what an intake looks like.

Your paths to evaluation include:

• Your primary care doctor or an obesity medicine specialist.
• A telehealth provider that offers asynchronous or video visits. Chia is one option among licensed telehealth providers — our clinicians review your intake, discuss FDA-approved and compounded options, and prescribe when clinically appropriate.

Whichever route you choose, be ready to discuss your full medical history, including any family history of thyroid cancer, pancreatitis, or eating disorders — these affect which medications are safe for you.

Frequently asked questions

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