Zepbound vs Ozempic

The two trials everyone quotes

Neither is Zepbound versus Ozempic. Each compares the molecules with one label swapped out.

SURMOUNT-5 is the only head-to-head weight-loss trial. It randomised 751 adults with obesity and no diabetes to the maximum tolerated dose of tirzepatide or semaglutide for 72 weeks. There was no placebo arm.

The catch is the semaglutide arm. It used 1.7 or 2.4 mg, which are Wegovy doses. Ozempic stops at 2 mg and is not approved for weight reduction. So SURMOUNT-5 is Zepbound versus Wegovy, and the Wegovy vs Zepbound page is where it belongs. Waist circumference fell 18.4 cm versus 13.0 cm, and more tirzepatide participants crossed every threshold from 10% to 25%.

SURPASS-2 is the closest thing to an Ozempic dose. It randomised 1,879 adults with type 2 diabetes to tirzepatide or semaglutide 1 mg for 40 weeks.

Tirzepatide was superior at every dose. Weight fell 7.6, 9.3, and 11.2 kg on 5, 10, and 15 mg against 5.7 kg on semaglutide. But this is a diabetes population, the tirzepatide here is sold as Mounjaro, and Zepbound is not approved for diabetes. It is the Ozempic vs Mounjaro comparison.

What each label is for

Zepbound’s indications come from the SURMOUNT program. In SURMOUNT-1, 15 mg produced 20.9% mean weight loss over 72 weeks against 3.1% on placebo. In SURMOUNT-OSA, apnea-hypopnea index fell by 25 to 29 events per hour against about 5 on placebo, which made Zepbound the first drug approved for sleep apnea.

Ozempic’s indications come from SUSTAIN and FLOW. In SUSTAIN-6, 6.6% of patients with type 2 diabetes had a major cardiovascular event on semaglutide versus 8.9% on placebo, hazard ratio 0.74. Zepbound has no cardiovascular indication. Its sibling Mounjaro does, from SURPASS-CVOT, where tirzepatide matched dulaglutide with a hazard ratio of 0.92.

Put together: a prescriber treating obesity has one of these on-label, and a prescriber treating diabetes has the other. The comparison people want, “which is stronger for weight loss”, crosses that line.

Mechanism

Semaglutide activates one receptor, GLP-1. Tirzepatide activates two, GLP-1 and GIP. Whether the second receptor explains the larger weight loss is still being worked out; the GLP-1 vs GLP-2 vs GLP-3 page covers what single, dual, and triple agonists mean.

Half-life is the practical difference. Tirzepatide clears in about five days, semaglutide in about seven. Semaglutide takes longer to reach steady state and stays in circulation for around five weeks after a last dose. The half-life visualizer models both.

What is identical

The boxed warning on thyroid C-cell tumors, the contraindication for medullary thyroid carcinoma history or MEN 2, and the warnings on pancreatitis, gallbladder disease, and severe gastrointestinal reactions appear on both labels in the same terms.

Which comparison you wanted

• The trial that exists, on the right labels: Wegovy vs Zepbound.
• Both diabetes labels: Ozempic vs Mounjaro.
• The molecules without the brands: semaglutide vs tirzepatide.
• Why Zepbound and Mounjaro are one drug: Zepbound vs Mounjaro.

Whichever molecule, log product, date, milligrams, and site. How GLP-1 tracking works covers what to record.

6. Zepbound vs Ozempic FAQ

• Is Zepbound better than Ozempic for weight loss?

  Weight reduction is not on the Ozempic label, so the question compares an approved use with an off-label one. The nearest data, SURMOUNT-5, found tirzepatide produced 20.2% weight loss versus 13.7% for semaglutide at Wegovy doses over 72 weeks. Ozempic doses were not tested.

• Has Zepbound ever been compared with Ozempic in a trial?

  No. SURMOUNT-5 compared tirzepatide with Wegovy-dose semaglutide in obesity. SURPASS-2 compared tirzepatide with semaglutide 1 mg in type 2 diabetes. Neither used the Zepbound and Ozempic labels together.

• What is the difference between tirzepatide and semaglutide?

  Semaglutide activates the GLP-1 receptor. Tirzepatide activates the GLP-1 receptor and the GIP receptor. Both are once-weekly injections. Tirzepatide's half-life is about 5 days; semaglutide's is about a week.

• Can I switch from Ozempic to Zepbound?

  Switching between molecules is a prescriber decision. There is no conversion table between the two dose ladders; each label starts at its own first step. The labels do not address switching from one to the other.

• Which one lowers heart attack risk?

  Ozempic carries a cardiovascular indication from SUSTAIN-6, where major events fell from 8.9% to 6.6% in type 2 diabetes. Zepbound does not carry one. Mounjaro, the diabetes brand of tirzepatide, does, from SURPASS-CVOT.

7. Sources