Getting diet pills depends on which type you’re after. The FDA has approved six medications for long-term weight management, and all but one require a prescription. The single exception, a lower-dose version of orlistat sold as Alli, is available over the counter at most pharmacies. Everything else, including the newer injectable medications that have dominated headlines, starts with a doctor’s visit.
Prescription vs. Over-the-Counter Options
Only one FDA-approved weight loss medication is sold without a prescription: Alli, a lower-dose version of orlistat that works in your gut to reduce the amount of fat your body absorbs from food. You can pick it up at any pharmacy or drugstore. Every other product marketed as a diet pill or weight loss supplement on store shelves is classified as a dietary supplement, not a medication. That distinction matters. Dietary supplements are not reviewed by the FDA for safety or effectiveness before they hit the market. Their labels are required to carry a disclaimer stating exactly that.
The FTC requires that advertising for supplements be truthful and backed by competent scientific evidence, but enforcement happens after products are already being sold. Including a disclaimer on the label doesn’t make misleading claims acceptable, but it does mean you’re largely on your own when evaluating whether a supplement actually works. If a product promises dramatic weight loss without diet or exercise, that’s a red flag, not a feature.
FDA-Approved Prescription Medications
Six prescription medications are approved for long-term weight management. They fall into three broad categories based on how they work and how you take them.
Oral medications (pills):
- Orlistat (Xenical) blocks fat absorption in the gut. Taken three times daily. Approved for adults and children 12 and older.
- Phentermine-topiramate (Qsymia) combines an appetite suppressant with an anti-seizure drug. Taken once daily. Approved for adults and children 12 and older.
- Naltrexone-bupropion (Contrave) pairs two medications originally used for addiction and depression to reduce hunger. Taken once or twice daily. Adults only.
Injectable medications (GLP-1 and related):
- Semaglutide (Wegovy) mimics a gut hormone that targets appetite centers in the brain. Weekly injection. Approved for adults and children 12 and older.
- Tirzepatide (Zepbound) targets two gut hormones instead of one. Weekly injection. Adults only.
- Liraglutide (Saxenda) works similarly to semaglutide but requires daily injection. Approved for adults and children 12 and older.
There’s also phentermine on its own, which is only approved for short-term use of a few weeks. It’s an older appetite suppressant that doctors sometimes prescribe as a starting point.
Who Qualifies for a Prescription
Doctors generally prescribe weight loss medication for people with a BMI of 30 or higher, or a BMI of 27 or higher combined with at least one weight-related health condition like high blood pressure, type 2 diabetes, or high cholesterol. These thresholds come from clinical guidelines, though individual doctors may apply some flexibility based on your overall health picture.
If you don’t meet those criteria, a prescription is unlikely. Weight loss medications carry real side effects and are designed for people whose weight poses a medical risk, not for losing a few vanity pounds.
What Happens at the Doctor’s Visit
At your first appointment, expect a conversation about your weight loss goals, your daily routine around food and exercise, how long you’ve been trying to lose weight, and your full medical history. Your doctor will want to understand whether you have conditions that would make certain medications unsafe. Phentermine, for example, is not appropriate for people with heart disease, high blood pressure, hyperthyroidism, or glaucoma. Older adults are generally steered away from it entirely.
You may leave that first visit with a prescription, or your doctor may order lab work first. Some providers want baseline blood panels to check thyroid function, blood sugar, and liver health before choosing a medication. The whole process can happen through your primary care doctor, an endocrinologist, or a weight management specialist. Telehealth services now offer these consultations remotely as well, which has made access easier for people in areas without nearby specialists.
Insurance Coverage and Cost
This is where things get frustrating. Many insurance plans either exclude weight loss medications entirely or layer on significant hurdles before approving coverage. Prior authorization is common, meaning your doctor has to submit documentation proving the medication is medically necessary before the insurer agrees to pay.
Some plans require documented failure of other approaches first. Michigan’s Medicaid program, for instance, requires that a patient be classified as morbidly obese, have tried and failed other weight loss interventions including preferred lower-cost drugs, and that coverage be considered only to prevent the need for bariatric surgery. Private insurers often impose similar step-therapy requirements.
Without insurance, costs vary dramatically. The injectable medications, particularly semaglutide and tirzepatide, can run over $1,000 per month at retail price. Oral options like naltrexone-bupropion and phentermine-topiramate tend to be less expensive, and some are available as generics. Manufacturer savings cards and patient assistance programs can help, but they usually exclude people on government insurance.
Avoiding Unsafe Sources
The popularity of GLP-1 medications has created a booming market for counterfeit and unregulated versions. The FDA has issued warnings about fraudulent compounded semaglutide and tirzepatide products showing up with fake pharmacy names on the labels, incorrect addresses, and spelling errors. In some cases, the pharmacies listed on the packaging don’t even exist.
Illegally marketed versions sold online may contain the wrong ingredients, harmful ingredients, or the wrong dose of the active ingredient. The FDA has sent warning letters to companies distributing these products, but new sellers appear constantly. If you’re purchasing from an online source, verify that it’s a state-licensed pharmacy and that you have a legitimate prescription from a licensed provider. Compounded versions of these drugs are only appropriate when the FDA-approved versions can’t meet a patient’s specific medical needs.
As of early 2025, the FDA has determined that the national shortages of both semaglutide and tirzepatide injections are resolved, meaning the branded products should be available through standard pharmacies. Some localized supply disruptions may still occur as products move through distribution chains, but the widespread shortages that drove many people toward compounded alternatives are no longer an issue.
Side Effects to Expect
Every weight loss medication comes with trade-offs. Orlistat commonly causes oily stools, gas, and urgent bowel movements, especially if you eat high-fat meals. These effects are uncomfortable but predictable and tend to improve as you adjust your diet.
Phentermine and medications containing it can cause increased blood pressure, heart palpitations, restlessness, insomnia, dizziness, and tremor. More serious symptoms like chest pain, shortness of breath, or leg swelling require immediate medical attention.
The GLP-1 injectable medications are best known for causing nausea, particularly during the first few weeks and after dose increases. Vomiting, diarrhea, and constipation are also common. Most people find these effects manageable and temporary, which is why doctors typically start at a low dose and increase gradually over several weeks or months.
Naltrexone-bupropion frequently causes nausea, headache, and constipation. Because it contains bupropion, it also carries a boxed warning about increased risk of suicidal thoughts, though this risk applies primarily to younger adults and is monitored closely.
Your doctor will typically schedule follow-up visits to track your progress, monitor side effects, and adjust your dose. Weight loss medications work best as part of a broader approach that includes changes to eating patterns and physical activity. They reduce the biological drive to eat, but they don’t replace the need for sustainable habits.