Weight loss drugs: what works and what to watch for

Want to lose weight with medication? You’re not alone. New drugs like semaglutide and tirzepatide are changing the game, but they aren’t magic. This page gives a clear, practical look at the main options, how they work, common side effects, and simple tips to stay safe and get the most from treatment.

Which drugs actually work?

Here are the main categories you’ll see:

GLP‑1 receptor agonists (injectables). Examples: semaglutide (Wegovy/Ozempic) and liraglutide (Saxenda). They slow stomach emptying, reduce appetite, and help many people lose 10% or more of body weight—semaglutide and tirzepatide trials often show double-digit losses over months.

Tirzepatide (Mounjaro) is a dual GIP/GLP‑1 drug. In recent trials it produced very large average weight losses—sometimes more than semaglutide—so it’s getting a lot of attention.

Orlistat (Xenical/Alli) is a pill that blocks fat absorption. Expect smaller weight changes than GLP‑1s but it’s a non‑injectable option. Side effects include oily stools and possible vitamin deficiencies.

Stimulant pills like phentermine are older, often used short-term for quick loss. They can raise heart rate and blood pressure and may cause insomnia or dependency if misused.

Combination pills such as bupropion‑naltrexone (Contrave) affect appetite and reward pathways and can help some people lose moderate weight.

Metformin isn’t primarily a weight drug, but research (including recent findings on an "anti‑hunger" molecule called lac‑Phe) shows it can reduce appetite for some people and is sometimes used off‑label.

Safety, cost, and everyday tips

Who should consider medication? Typically people with BMI ≥30, or BMI ≥27 with a weight‑related condition like type 2 diabetes or high blood pressure. That said, a doctor should decide case by case.

Watch for common side effects: nausea, vomiting, diarrhea, constipation, and loss of appetite with GLP‑1s; gallstones and pancreatitis are less common but serious. Orlistat mainly causes digestive issues. Stimulants can affect heart rate and sleep. Pregnant people should avoid these drugs.

Costs vary a lot. New injections can be expensive and may need prior authorization from insurers. Ask about generic options, patient programs, or alternatives like orlistat.

Practical tips: set realistic goals (5–15% body weight is typical), plan to combine medication with diet and activity, and expect weight regain if the drug is stopped. Get baseline labs (glucose, liver, lipids) and regular checkups. Tell your provider about other meds—some combinations can cause low blood sugar or other risks.

If you want specifics for your case, talk to a clinician who knows obesity care. Meds help a lot for many people, but they work best with a plan and regular follow‑up.