Appetite suppressants compared from FDA labels: phentermine, Qsymia, Contrave and GLP-1s, plus supplement claims rated and FDA tainted-product warnings.
Fact-checked against FDA labels and official sources; not yet reviewed by a licensed clinician. This page is education, not medical advice. Talk to your doctor before starting, stopping or changing any treatment.
Key takeaways
- Phentermine is labeled only for short-term use (a few weeks); its own label calls the extra weight loss over diet alone "clinically limited".[1]
- At one year, Qsymia's top dose produced 9.8% to 10.9% average weight loss vs 1.2% to 1.6% on placebo; it can harm a developing baby and is dispensed through a REMS program.[2]
- Contrave produced 5.4% vs 1.3% in COR-I and carries a boxed warning about suicidal thoughts; it is not for people with seizures or chronic opioid use.[3]
- The FDA does not approve dietary supplements, and has found weight-loss products hiding sibutramine and other drugs.[8]
- Pooled trials show supplement effects of roughly 0 to 2 kg vs placebo, compared with 12.7 kg for Wegovy in STEP 1.[18]
In short: The medicines with real evidence for reducing appetite and weight are prescription drugs reviewed by the FDA: phentermine (short-term only), Qsymia (phentermine plus topiramate), Contrave (naltrexone plus bupropion) and the GLP-1 medicines such as Wegovy, Zepbound and Foundayo. Supplements sold as “appetite suppressants” are not FDA approved, most have little or no evidence, and the FDA keeps finding some that secretly contain prescription or banned drugs. High-fiber, high-protein meals can also help you feel full (checked on 2026-10-06).
This guide compares the prescription options using their FDA labels: who each is for in general terms, how they work, what the trials showed, side effects, boxed warnings and who should not take them. Then it rates the supplement claims and explains the FDA’s tainted-product warnings. It is information only. InstaTuck sells nothing here and links to no sellers; the right choice, if any, depends on an evaluation by a licensed clinician. Please research, ask questions and get checked before you take anything to curb your appetite.
Prescription options at a glance
| Medicine | FDA status | Labeled for (general terms) | Key label points |
|---|---|---|---|
| Phentermine (for example Lomaira, generics) | FDA approved, short-term | A few weeks, as part of a diet, exercise and behavior program, for people with obesity (BMI 30+, or 27+ with other risk factors such as controlled high blood pressure, diabetes or high cholesterol) | Schedule IV; related to amphetamine; not with heart disease, uncontrolled high blood pressure, hyperthyroidism, glaucoma, agitation, drug-abuse history, pregnancy, nursing or MAOIs |
| Qsymia (phentermine and topiramate) | FDA approved for weight management | Adults and children 12+ with obesity; adults with overweight plus a weight-related condition; long term | Can harm a developing baby: pregnancy test before and monthly; REMS program; not with glaucoma, hyperthyroidism or MAOIs |
| Contrave (naltrexone and bupropion) | FDA approved for weight management | Adults with obesity, or overweight plus a weight-related condition; long term | Boxed warning on suicidal thoughts and behaviors; not with uncontrolled high blood pressure, seizures, eating disorders, chronic opioid use or MAOIs |
| GLP-1 medicines: Wegovy, Zepbound, Foundayo, Saxenda | FDA approved for weight management | Adults (some also teens) with obesity, or overweight plus a weight-related condition | Boxed warning on thyroid C-cell tumors in rodents; mainly digestive side effects |
Phentermine: the classic short-term appetite suppressant
Phentermine is a sympathomimetic amine, chemically and pharmacologically related to amphetamine. The Lomaira label says it is indicated only as a short-term (“a few weeks”) add-on to a weight-reduction program based on exercise, behavior change and calorie restriction. The label itself is candid about its limits: in short trials, people taking “anorectic” drugs lost more weight than people on placebo and diet, but the extra loss was “only a fraction of a pound a week”, the rate of loss was greatest in the first weeks, and the total impact over diet alone “must be considered clinically limited”. It also notes that tolerance to the appetite effect can develop, and that the dose should not be raised to chase it; instead the drug should be stopped.
Side effects listed on the label include a racing or pounding heartbeat, higher blood pressure, restlessness, insomnia, dizziness, tremor, headache, dry mouth, unpleasant taste and digestive upset. Rare but serious reports include primary pulmonary hypertension and heart-valve disease, mostly when phentermine was combined with fenfluramine or dexfenfluramine (“fen-phen”). It is a Schedule IV controlled substance with a potential for abuse, and the label says not to combine it with other weight-loss drugs, including over-the-counter and herbal products.
Qsymia: phentermine plus topiramate
Qsymia pairs a lower dose of phentermine with extended-release topiramate, a seizure and migraine medicine. In the two one-year trials in its label, adults on the top dose (15 mg/92 mg) lost 10.9% of their weight in Study 1 (people with obesity) versus 1.6% on placebo, and 9.8% in Study 2 (people with obesity or overweight plus two or more conditions) versus 1.2%. In Study 2, 70% of people on the top dose lost at least 5% of their weight, compared with 21% on placebo.
Qsymia is a once-daily capsule taken in the morning; the label says to avoid evening doses because of insomnia, and to start at the lowest strength for 14 days before stepping up. The label’s step plan is built around response: after 12 weeks on the top dose, an adult who has not lost at least 5% of their starting weight should stop, and the top dose is tapered off gradually to avoid a possible seizure. The most common side effects were tingling (paresthesia), dry mouth, constipation, altered taste, insomnia and dizziness. Warnings include harm to a developing baby (the label recommends a negative pregnancy test before starting and monthly during treatment, effective contraception, and dispensing through a REMS safety program), suicidal thoughts (topiramate is an antiepileptic drug), sudden nearsightedness and angle-closure glaucoma, mood and sleep problems, trouble with attention or memory, slowed growth in children, metabolic acidosis and reduced kidney function. Phentermine makes Qsymia a Schedule IV controlled substance.
| Item | Qsymia 15 mg | 92 mg | Qsymia 7.5 mg |
|---|---|---|---|
| Tingling (paresthesia) | 20% | 14% | 2% |
| Dry mouth | 19% | 14% | 3% |
| Constipation | 16% | 15% | 6% |
| Dizziness | 9% | 7% | 3% |
| Altered taste (dysgeusia) | 9% | 7% | 1% |
| Insomnia | 9% | 6% | 5% |
Source: Qsymia prescribing information, Table 1 (DailyMed, revised April 2026) (checked on October 6, 2026)
Contrave: naltrexone plus bupropion
Contrave combines naltrexone, an opioid blocker, with bupropion, an antidepressant ingredient. In its label’s three 56-week trials, average weight change was -5.4% versus -1.3% on placebo in COR-I, -8.1% versus -4.9% in COR-BMOD (which added an intensive behavior program to both groups) and -3.7% versus -1.7% in COR-Diabetes. In COR-I, 42% of people on Contrave lost at least 5% of their weight versus 17% on placebo. Many people left the trials early: 46% on Contrave and 45% on placebo did not reach week 56. Contrave tablets are stepped up over four weeks, from one tablet in the morning in week 1 to two tablets twice a day from week 4, according to the label. The label says to check response after 12 weeks on the maintenance dose and stop if a person has not lost at least 5%, as it is unlikely they will reach and keep a meaningful weight loss.
Because bupropion is also an antidepressant, Contrave carries a boxed warning about suicidal thoughts and behaviors in children, teens and young adults taking antidepressants; it is not approved for anyone under 18. Other warnings include seizures (risk is lowered by following the dosing schedule and not taking it with a high-fat meal), increases in blood pressure and heart rate, liver injury with naltrexone, angle-closure glaucoma and low blood sugar in people on diabetes medicines. It is contraindicated with uncontrolled high blood pressure, seizure disorders, anorexia or bulimia, abruptly stopping alcohol, benzodiazepines, barbiturates or seizure medicines, other bupropion products, chronic opioid use and MAOIs. It can also cause a false-positive urine test for amphetamines.
| Item | Contrave | Placebo |
|---|---|---|
| Nausea | 32.5% | 6.7% |
| Constipation | 19.2% | 7.2% |
| Headache | 17.6% | 10.4% |
| Vomiting | 10.7% | 2.9% |
| Dizziness | 9.9% | 3.4% |
| Insomnia | 9.2% | 5.9% |
| Dry mouth | 8.1% | 2.3% |
Source: Contrave prescribing information, Table 3 (DailyMed, revised November 2025) (checked on October 6, 2026)
Our Contrave vs Qsymia comparison puts these two side by side.
GLP-1 medicines: appetite through gut hormones
GLP-1 medicines are not usually called “appetite suppressants”, but reducing appetite is how they work: the Wegovy and Foundayo labels say these medicines decrease food or calorie intake, likely through effects on appetite. In STEP 1, adults on weekly semaglutide 2.4 mg (Wegovy) lost 14.9% of their weight at 68 weeks versus 2.4% on placebo; in Foundayo’s Trial 1, adults on the daily 17.2 mg pill lost 11.1% at 72 weeks versus 2.1%. See our GLP-1 medications guide, the oral GLP-1 pills guide and weight-loss injections.
| Item | Medicine | Placebo |
|---|---|---|
| Wegovy 2.4 mg, STEP 1 (68 weeks) | 14.9% | 2.4% |
| Foundayo 17.2 mg, Trial 1 (72 weeks) | 11.1% | 2.1% |
| Qsymia 15/92 mg, Study 1 (1 year) | 10.9% | 1.6% |
| Qsymia 15/92 mg, Study 2 (1 year) | 9.8% | 1.2% |
| Contrave, COR-I (56 weeks) | 5.4% | 1.3% |
Different trials, people and lengths: these numbers are not a ranking. Contrave: DailyMed setid 485ff360-32c8-11df-928b-0002a5d5c51b; STEP 1: doi.org/10.1056/NEJMoa2032183.
Source: Qsymia, Contrave and Foundayo labels (DailyMed); STEP 1, NEJM 2021 (checked on October 6, 2026)
Choosing between them: what the labels make you weigh
| Question | Phentermine | Qsymia | Contrave | GLP-1 medicines |
|---|---|---|---|---|
| Length of use on the label | Short term (a few weeks) | Long term | Long term | Long term |
| Controlled substance | Yes, Schedule IV | Yes, Schedule IV | No | No |
| Pregnancy | Contraindicated | Contraindicated; monthly tests; REMS | Stop when pregnancy is recognized | Stop when pregnancy is recognized |
| Stop rule if little loss | Stop if tolerance develops | Under 5% after 12 weeks on top dose | Under 5% after 12 weeks on maintenance | Set by the prescriber |
| Main cautions | Heart disease, blood pressure, glaucoma, hyperthyroidism, abuse potential | Harm to a developing baby, mood, eyes, metabolic acidosis, kidney stones | Suicidal thoughts warning, seizures, blood pressure, opioids | Thyroid C-cell tumor warning, pancreatitis, gallbladder, digestive effects |
Medicines that were withdrawn
Two former appetite medicines show why safety follow-up matters. Sibutramine (Meridia), approved in 1997, was withdrawn from the U.S. market in December 2010 after data showed a higher risk of heart attack and stroke, according to the FDA. In 2020 the FDA asked the maker of lorcaserin (Belviq and Belviq XR) to withdraw it after a safety trial showed more cancer, concluding that its risks outweighed its benefits. Both matter today because sibutramine keeps turning up hidden in “natural” supplements (see below).
Supplement claims, rated
By law, the FDA does not approve dietary supplements for safety or effectiveness before they are sold. The NIH’s National Center for Complementary and Integrative Health (NCCIH) says many supplements marketed for weight loss, including those sold as appetite suppressants, have not been tested for safety. Here is what pooled trials and NIH reviews show for common appetite and weight claims:
| Ingredient | Claim | What the evidence shows | Key safety notes |
|---|---|---|---|
| Glucomannan | Swells, fills you up | Pooled 8 trials: 0.22 kg more loss than placebo, not significant (2014) | Abdominal discomfort, diarrhea, constipation |
| Psyllium | Fullness before meals | Mixed: one 2023 analysis of 6 trials found 2.1 kg; a 2020 analysis of 22 trials found no significant effect | Choking risk without enough fluid; take other medicines 2 hours apart |
| Garcinia cambogia (HCA) | Blocks appetite and fat | Pooled 9 trials: 0.88 kg, small and of uncertain relevance (2011) | Digestive effects |
| Green tea extract | Burns fat, curbs hunger | Cochrane: no meaningful effect outside Japan (-0.04 kg) | Rare liver injury with extracts |
| Bitter orange (synephrine) | Ephedra-like appetite and energy | Effects on weight unclear (NCCIH) | Reports of heart rhythm problems, heart attacks and strokes with multi-ingredient products |
| Berberine | “Nature’s Ozempic” | Small pooled effects (about 0-2 kg), inconsistent | Drug interactions, including with cyclosporine and diabetes medicines |
The tainted-product problem
The FDA warns that products marketed as dietary supplements or “all natural” weight-loss aids may contain hidden drug ingredients removed from the market for safety reasons. Its laboratory tests have found sibutramine, fenproporex, fluoxetine, bumetanide, furosemide, phenytoin, rimonabant, cetilistat and phenolphthalein in weight-loss products sold over the counter. On September 15, 2026 it warned consumers not to use a product sold online for weight loss that contained undeclared sibutramine, which can significantly raise blood pressure and heart rate and interact dangerously with other medicines. The FDA says it cannot test every product, that its database covers only a small fraction of contaminated products, and that such products increasingly appear in popular online marketplaces, social media ads and stores.
Food-based ways to feel fuller
Food choices can support fullness without a pill. A 2020 meta-analysis of 62 trials found that adding viscous (gel-forming) fiber to an unrestricted diet lowered body weight by an average of 0.33 kg, a modest effect with moderate-certainty evidence. The FDA Daily Value for fiber is 28 g a day. Our guides to high-protein eating, healthy snacks and the calorie deficit show how to build filling meals, and emotional eating covers hunger that is not about the stomach.
Before trying any appetite product
- Name the problemConstant hunger, evening snacking, emotional eating and medication side effects need different approaches.
- Check the badgeFDA approved for weight management, approved for another use, or a dietary supplement that is not FDA approved.
- List your medicinesPhentermine, Qsymia and Contrave all interact with MAOIs and other drugs; supplements interact too.
- Get evaluatedA clinician checks blood pressure, heart health, mood, pregnancy plans and other conditions first.
- Plan the long termThe labels expect diet and activity changes alongside any medicine.
For every approved pill in one place, see weight-loss pills; for clinicians who can prescribe, see the medical weight loss guide. Use the BMI calculator before your visit, and the medications hub to look up any medicine’s FDA status.
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- Is my hunger likely physical, emotional, or a side effect of a medicine I take?
- Which prescription options are appropriate given my blood pressure, heart health, mood and pregnancy plans?
- Do any of my current medicines or supplements interact with these drugs?
- How will we judge whether it is working, and when would we stop?
- What does my insurance cover, and what would it cost me?
Frequently asked questions
What is the strongest appetite suppressant?
There is no single "strongest" one for everyone. The medicines with the most evidence for weight loss are FDA-approved prescription drugs such as GLP-1 medicines, Qsymia and Contrave. Which, if any, fits you depends on your health and is a decision for you and a clinician.
Is phentermine safe long term?
Phentermine alone is labeled only for short-term use of a few weeks. Qsymia contains a lower dose of phentermine combined with topiramate and is approved for long-term use. Both are Schedule IV controlled substances.
Are there over-the-counter appetite suppressants that work?
Supplements sold as appetite suppressants are not FDA approved. Alli, a lower-dose orlistat, is an over-the-counter weight-loss aid with an FDA Drug Facts label for overweight adults 18 and older, but it works in the gut by blocking some fat absorption, not on appetite.
Does glucomannan or psyllium curb appetite?
These fibers swell with water, and some trials suggest small effects, but pooled results are mixed: glucomannan showed no significant weight loss in a 2014 review, and psyllium results differ between reviews. Take them with plenty of water.
Is berberine a natural Ozempic?
No. Berberine is a plant compound sold as a supplement. Pooled trials show small and inconsistent effects on weight, far smaller than with approved GLP-1 medicines, and it can interact with prescription drugs.
Why are some weight-loss supplements dangerous?
The FDA has found products hiding sibutramine, a drug withdrawn for heart risks, plus diuretics, antidepressants and laxatives no longer considered safe. Some stimulant ingredients raise heart rate and blood pressure.
Can I take an appetite suppressant with a GLP-1?
The phentermine label says the safety of combining it with other weight-loss drugs has not been established, and the Qsymia label says the same about other weight-loss products. Do not combine products without your prescriber.
Do appetite suppressants work after you stop?
Often not. In the STEP 1 extension, people who stopped semaglutide regained about two thirds of the weight they had lost within a year. That is why the labels pair medicines with lasting diet and activity changes. Plan the long term with your clinician.
References
- LOMAIRA (phentermine hydrochloride) tablets: prescribing information. via DailyMed. (accessed October 6, 2026) Drug label
- QSYMIA (phentermine and topiramate) extended-release capsules: prescribing information. Vivus, via DailyMed, 2026. (accessed October 6, 2026) Drug label
- CONTRAVE (naltrexone HCl and bupropion HCl) extended-release tablets: prescribing information. Nalpropion Pharmaceuticals, via DailyMed, 2025. (accessed October 6, 2026) Drug label
- WEGOVY (semaglutide) injection and tablets: prescribing information. Novo Nordisk, via DailyMed, 2026. (accessed October 7, 2026) Drug label
- FOUNDAYO (orforglipron) tablets: prescribing information. Eli Lilly and Company, via DailyMed, 2026. (accessed October 7, 2026) Drug label
- Wilding JPH, Batterham RL, Calanna S, et al.. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). New England Journal of Medicine, 2021. doi:10.1056/NEJMoa2032183 · PMID 33567185 · NCT03548935 (accessed October 7, 2026) Randomized trial
- FDA requests the withdrawal of the weight-loss drug Belviq, Belviq XR (lorcaserin) from the market. U.S. Food and Drug Administration, 2020. (accessed October 6, 2026) Government page
- Questions and answers about FDA’s initiative against contaminated weight loss products. U.S. Food and Drug Administration. (accessed October 6, 2026) Government page
- FDA notification: weight-loss product may be harmful due to hidden ingredient (sibutramine). U.S. Food and Drug Administration, 2026. (accessed October 6, 2026) Government page
- Avoiding products contaminated with hidden ingredients. U.S. Food and Drug Administration. (accessed October 6, 2026) Government page
- Is it really ‘FDA approved’?. U.S. Food and Drug Administration. (accessed October 7, 2026) Government page
- 6 Things To Know About Dietary Supplements Marketed for Weight Loss. National Center for Complementary and Integrative Health (NIH). (accessed October 6, 2026) Government page
- Bitter orange: usefulness and safety. NCCIH (NIH). (accessed October 6, 2026) Government page
- Onakpoya I, Posadzki P, Ernst E. The efficacy of glucomannan supplementation in overweight and obesity. Journal of the American College of Nutrition, 2014. doi:10.1080/07315724.2014.870013 · PMID 24533610 (accessed October 7, 2026) Meta-analysis
- Gibb RD, Sloan KJ, McRorie JW. Psyllium is a natural nonfermented gel-forming fiber that is effective for weight loss: a comprehensive review and meta-analysis. Journal of the American Association of Nurse Practitioners, 2023. doi:10.1097/JXX.0000000000000882 · PMID 37163454 (accessed October 7, 2026) Meta-analysis
- Darooghegi Mofrad M, Mozaffari H, Mousavi SM, et al.. The effects of psyllium supplementation on body weight, body mass index and waist circumference in adults: a systematic review and dose-response meta-analysis. Critical Reviews in Food Science and Nutrition, 2020. doi:10.1080/10408398.2018.1553140 · PMID 30880409 (accessed October 7, 2026) Meta-analysis
- Onakpoya I, Hung SK, Perry R, Wider B, Ernst E. The use of Garcinia extract (hydroxycitric acid) as a weight loss supplement. Journal of Obesity, 2011. PMID 21197150 (accessed October 6, 2026) Meta-analysis
- Jurgens TM, Whelan AM, Killian L, et al.. Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane Database of Systematic Reviews, 2012. doi:10.1002/14651858.CD008650.pub2 · PMID 23235664 (accessed October 7, 2026) Meta-analysis
- Elahi Vahed I, Shahir-Roudi E, Nojumi S, et al.. The effect of berberine on obesity indices: a systematic review and meta-analysis. International Journal of Obesity, 2026. doi:10.1038/s41366-025-01943-x · PMID 41310257 (accessed October 6, 2026) Meta-analysis
- Jovanovski E, Mazhar N, Komishon A, et al.. Can dietary viscous fiber affect body weight independently of an energy-restrictive diet?. American Journal of Clinical Nutrition, 2020. doi:10.1093/ajcn/nqz292 · PMID 31897475 (accessed October 7, 2026) Meta-analysis
- Wilding JPH, Batterham RL, Davies M, et al.. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes, Obesity and Metabolism, 2022. doi:10.1111/dom.14725 · PMID 35441470 (accessed October 7, 2026) Randomized trial
- ALLI (orlistat 60 mg) capsules: Drug Facts. Haleon, via DailyMed, 2026. (accessed October 6, 2026) Drug label
- Daily Value on the Nutrition and Supplement Facts Labels. U.S. Food and Drug Administration. (accessed October 7, 2026) Government page
Facts checked on October 6, 2026
Educational information, not medical advice. Talk with a qualified healthcare professional about your own situation. In an emergency call 911.