Direct Comparison of Today’s Leading Prescription Weight Loss Drugs
Below, we break down semaglutide, tirzepatide, and liraglutide—the most-requested GLP-1 and GIP/GLP-1 therapies—alongside orlistat and phentermine/topiramate. Each card is based on prescribing experience and current evidence, not just manufacturer claims.
For full context, see our detailed weight loss drugs guide or compare prescription options.
Semaglutide (Wegovy®, Ozempic®)
Semaglutide is a weekly injectable prescription originally designed for type 2 diabetes, now widely used for weight management under the brand name Wegovy®. In real-world obesity clinics, it is the most requested GLP-1 due to its strong results and insurance coverage improving in 2024.
- Who it’s for: Adults with BMI ≥30, or ≥27 with weight-related conditions.
- What to expect: Typical loss of 10–16% body weight in 6–12 months, with strongest results when paired with lifestyle support.
- Common side effects: Nausea (up to 40%), mild GI upset, rare risk of pancreatitis.
- Unique: Once-weekly dosing, most robust clinical data, but can plateau if doses are reduced.
Tirzepatide (Zepbound™, Mounjaro®)
Tirzepatide is the first dual GIP and GLP-1 receptor agonist, setting new benchmarks in both blood sugar and weight loss. In specialty clinics, it's in high demand for rapid, pronounced effects—sometimes outpacing semaglutide for those who tolerate it well.
- Who it’s for: Adults with BMI ≥30 or ≥27 with comorbidities, especially those with insulin resistance.
- What to expect: Average 15–21% weight loss in 52–72 weeks. Initial loss may be faster than with semaglutide.
- Common side effects: GI symptoms, appetite loss, some reports of injection site redness. Nausea risk similar to semaglutide, but ~8% more likely to discontinue due to side effects.
- Unique: May trigger more rapid early weight loss; insurance coverage still catching up in some regions.
Liraglutide (Saxenda®)
Liraglutide is a daily GLP-1 agonist, preceding semaglutide. Still widely prescribed when weekly options aren’t covered, it’s valued for a more gradual onset but typically achieves less overall weight loss.
- Who it’s for: Adults and adolescents ≥12 with obesity or specific risk factors.
- What to expect: Average 6–9% weight loss in a year, often slower than newer options.
- Common side effects: GI discomfort, nausea (less pronounced than semaglutide), rare gallbladder issues.
- Unique: Daily injection; established safety history in adolescents as well as adults.
Orlistat (Alli®, Xenical®)
Orlistat is the only over-the-counter weight loss medication with FDA approval. Unlike hormone modulators, it blocks fat absorption in the gut. Still recommended for some patients needing non-systemic options or for whom injectables are inappropriate.
- Who it’s for: Adults needing a non-prescription or budget-friendly approach; often used if unable to tolerate GLP-1s.
- What to expect: 3–7% weight loss with regular use and dietary management; results much slower and smaller than injectable options.
- Common side effects: Oily stools, GI urgency, especially with high-fat meals; no effect on appetite or cravings.
- Unique: OTC version (Alli) available, but success highly diet-dependent.
Phentermine/Topiramate (Qsymia®)
This oral combination has been prescribed for a decade, blending an appetite suppressant (phentermine) with a neurostabilizer (topiramate). Still trusted by some for patients unable to afford newer injectables, but with a distinct side effect profile.
- Who it’s for: Adults with BMI ≥30 or ≥27 and comorbidities; avoid if history of heart disease or certain psychiatric conditions.
- What to expect: 7–12% weight loss in the first year; many see most results within first 24–28 weeks.
- Common side effects: Insomnia, tingling, dry mouth, possible mood change; requires careful physician monitoring.
- Unique: Oral pill, daily dosing; may be more accessible for some with insurance or cost barriers.
What to Consider When Choosing a Weight Loss Medication
Selecting the right medication isn’t about picking the “strongest.” Our clinical team sees that patient fit—your medical background, insurance, and even side effect tolerance—matters more than average trial results. For instance, some excel on liraglutide’s slower pace, while others need early motivation from tirzepatide’s rapid progress. Some prefer oral pills for comfort or cost, even if injectable drugs show higher average results.
Remember: weight loss drugs work best with physician guidance, routine check-ins, and sustainable lifestyle adjustments. For details on how insurance coverage, dosage adjustments, and combination therapy play out in practice, see our prescription weight loss drugs guide.
- Insurance and Cost: Newer drugs can cost over $900/month before coverage; generic options may be <$50.
- Administration: Weekly or daily injection vs. oral pill; choose what fits your routine.
- Side Effects: Nausea is common on GLP-1s. Orlistat causes GI symptoms tied to diet. Phentermine/topiramate can affect sleep/mood.
- Speed of Results: Fast (tirzepatide), moderate (semaglutide), or gradual (liraglutide/orlistat).
- Long-term Use: Most require continued use for maintained results; stopping can mean regaining some weight unless habits change.
How Our Comparison Is Different
This page is built on direct physician experience—having guided hundreds of patients through these medications, including handling insurance appeals, dose titration, and troubleshooting rare side effects. Unlike broad summaries, we focus on what actually works for real people, not just what’s implied by clinical averages or marketing. If you want a more exhaustive survey, see our obesity medications overview.