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Semaglutide vs Tirzepatide (2026): Weight Loss, T2D, Cost

Semaglutide (semaglutide, Novo Nordisk) vs Tirzepatide (tirzepatide, Eli Lilly)

Last verified 2026-05-27

The verdict

Tirzepatide is the stronger weight-loss molecule: SURMOUNT-5, the only head-to-head obesity RCT, showed -20.2% body weight at 72 weeks vs semaglutide's -13.7%. Tirzepatide's dual GIP/GLP-1 mechanism also beat semaglutide on A1C and weight in SURPASS-2 (type 2 diabetes). Semaglutide retains the cardiovascular advantage from SELECT, where it cut MACE 20% in non-diabetic obesity. Choose tirzepatide for magnitude, semaglutide for proven CV risk reduction.

Side-by-side comparison

FieldSemaglutideTirzepatide
Head-to-head obesity trial (SURMOUNT-5, 72 wk)-13.7% body weight-20.2% body weight
Obesity pivotal trial (TBWL)-14.9% / 68 wk (STEP-1)-20.9% / 72 wk (SURMOUNT-1)
Type 2 diabetes head-to-headSUSTAIN-7: -6.5 kg (sema 1.0 mg, vs dulaglutide)SURPASS-2: -11.2 kg (tirz 15 mg) vs sema 1 mg -5.7 kg
MechanismGLP-1 receptor agonistDual GIP / GLP-1 receptor agonist
FDA-approved brandsOzempic (T2D), Wegovy (obesity/CV), Rybelsus (oral T2D)Mounjaro (T2D), Zepbound (obesity/OSA)
Cardiovascular outcome trialSELECT: MACE -20% in obesity without diabetesSURPASS-CVOT readout pending 2027
Compounded availability (2026)Widely available via 503A/503B pharmaciesAvailable but narrower supply; FDA shortage resolved Dec 2024
Cash price (manufacturer direct, monthly)$349-$499 (Wegovy NovoCare); $499 (Ozempic via NovoCare)$349-$499 (Zepbound LillyDirect)

Frequently asked questions

Is tirzepatide more effective than semaglutide for weight loss?

Yes, by a clear margin. SURMOUNT-5, the only head-to-head RCT in obesity, showed tirzepatide reduced body weight 20.2% vs semaglutide's 13.7% at 72 weeks (Aronne 2025 NEJM, PMID 40353578) — a 6.5-percentage-point gap that is both statistically significant and clinically meaningful. Cross-trial comparisons of the obesity pivotals (SURMOUNT-1 vs STEP-1) showed a similar pattern. Tirzepatide's dual GIP/GLP-1 mechanism appears to drive the larger appetite-suppression and energy-expenditure effects.

Is one better for type 2 diabetes?

Tirzepatide outperformed semaglutide head-to-head in T2D. SURPASS-2 (Frias 2021 NEJM, PMID 34170647) compared tirzepatide 5/10/15 mg to semaglutide 1 mg over 40 weeks: tirzepatide 15 mg lowered A1C by 2.30% and weight by 11.2 kg, vs semaglutide's 1.86% A1C drop and 5.7 kg loss. Both are once-weekly subcutaneous injections. Semaglutide remains preferred when a documented cardiovascular benefit (per SELECT) is the primary driver.

Which has better cardiovascular outcomes evidence?

Semaglutide. The SELECT trial (Lincoff 2023 NEJM, PMID 37952131) randomized 17,604 adults with obesity and established CV disease without diabetes; semaglutide 2.4 mg cut major adverse cardiovascular events (MACE) by 20% vs placebo over a mean 39.8 months. Tirzepatide's dedicated cardiovascular-outcome trial (SURPASS-CVOT) is still enrolling and won't read out until 2027. Until then, semaglutide is the only GLP-1 with an FDA-approved CV risk-reduction indication in non-diabetic obesity.

How do the mechanisms differ?

Semaglutide is a pure GLP-1 receptor agonist — it mimics glucagon-like peptide-1, which slows gastric emptying, blunts appetite, and stimulates glucose-dependent insulin release. Tirzepatide is a dual agonist hitting both GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors. GIP activation appears to amplify GLP-1's weight-loss effect and may reduce nausea by altering central appetite circuits, helping explain tirzepatide's larger magnitude on weight and A1C in head-to-head trials (SURMOUNT-5, SURPASS-2).

Can I get either as a compounded version?

Both are available compounded, but availability differs. Compounded semaglutide remains widely accessible through 503A and 503B pharmacies despite Novo Nordisk's shortage resolution in February 2025; the FDA's enforcement-discretion window closed for most 503Bs in May 2025 but personalized 503A compounding continues. Compounded tirzepatide is narrower — Eli Lilly's shortage was declared resolved in December 2024, and many compounders have stopped, though some still produce it for patient-specific clinical needs. Cash prices typically run $150-$400/month.

What are the side-effect differences?

Side-effect profiles are similar — both are dominated by gastrointestinal effects (nausea, diarrhea, constipation, vomiting). In SURMOUNT-5, tirzepatide actually had lower nausea (29%) than semaglutide (44%), though discontinuation due to adverse events was slightly higher with tirzepatide (8% vs 6%). Both carry the same FDA boxed warning for thyroid C-cell tumors based on rodent data, and both have small signals for pancreatitis, gallbladder disease, and acute kidney injury via dehydration. Titrate slowly to minimize GI tolerability problems.

References

References

  1. 1.Aronne LJ, Horn DB, le Roux CW, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5). N Engl J Med. 2025. PMID: 40353578.
  2. 2.Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021. PMID: 33567185.
  3. 3.Frias JP, Davies MJ, Rosenstock J, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). N Engl J Med. 2021. PMID: 34170647.
  4. 4.Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. Semaglutide and Cardiovascular Outcomes in Obesity Without Diabetes (SELECT). N Engl J Med. 2023. PMID: 37952131.
  5. 5.Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022. PMID: 35658024.
  6. 6.Pratley RE, Aroda VR, Lingvay I, et al. Semaglutide versus dulaglutide once weekly in patients with type 2 diabetes (SUSTAIN 7). Lancet Diabetes Endocrinol. 2018. PMID: 29397376.

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