Medication · US & Canada
Tirzepatide, explained
By Joshua Nichvolodoff · Fact-checked against sources November 2, 2026 · Next review due May 1, 2027
Clinical review: not yet reviewed by a clinician. How review works · Editorial policy
Tirzepatide is a dual GIP and GLP-1 receptor agonist made by Eli Lilly. Mounjaro and Zepbound are the same molecule under two brand names, authorized for different uses[1][2].
Status in the US and Canada
| Item | United States | Canada |
|---|---|---|
| Mounjaro | Type 2 diabetes (adults and children 10+); heart-risk reduction in type 2 diabetes | Type 2 diabetes (adults and children 10 to under 18) |
| Zepbound | Weight management; moderate-to-severe sleep apnea with obesity | Weight management (adults); sleep apnea with obesity, added June 2026 |
Same molecule, different labels
Both brands are once-weekly injections in the same 2.5 to 15 mg strengths[1][2]. Which brand is prescribed depends on the reason it is prescribed, and that affects how it is covered — see Mounjaro & Zepbound cost.
The labels say that using tirzepatide together with another tirzepatide product, or with any GLP-1 receptor agonist, is not recommended[2][4].
The trials behind it
Four major tirzepatide trials, with results for both groups, design limits and funding.
Study: SURMOUNT-1[6]
How much weight loss does weekly tirzepatide produce compared with placebo in adults with obesity and no diabetes?
- Who was in it
- 2,539 adults with a BMI of 30 or more, or 27 or more with a weight-related complication, without diabetes
- What they got
- Tirzepatide 5, 10 or 15 mg injection once a week, with lifestyle counselling
- Compared with
- Placebo, with lifestyle counselling
- How long
- 72 weeks
- What happened
- Average weight change: −15.0% (5 mg), −19.5% (10 mg), −20.9% (15 mg) vs −3.1% on placebo.
- Limits
- People with diabetes were excluded
- 72 weeks: no heart outcomes
- Did not test what happens after stopping
- Funded by
- Eli Lilly
Summary by Joshua Nichvolodoff, from the published paper — not written by the study's authors. Clinical review: not yet reviewed by a clinician.
Study: SURPASS-2[7]
Does tirzepatide lower blood sugar (HbA1c) more than semaglutide 1 mg in type 2 diabetes treated with metformin?
- Who was in it
- 1,879 adults with type 2 diabetes not controlled on metformin
- What they got
- Tirzepatide 5, 10 or 15 mg once a week
- Compared with
- Semaglutide 1 mg once a week
- How long
- 40 weeks
- What happened
- HbA1c fell 2.01, 2.24 and 2.30 percentage points on tirzepatide 5, 10 and 15 mg vs 1.86 on semaglutide 1 mg. Extra weight loss vs semaglutide: 1.9, 3.6 and 5.5 kg.
- Limits
- Open-label: participants knew which drug they took
- Semaglutide compared at 1 mg, not higher doses approved later
- 40 weeks
- Funded by
- Eli Lilly
Summary by Joshua Nichvolodoff, from the published paper — not written by the study's authors. Clinical review: not yet reviewed by a clinician.
Study: SURMOUNT-OSA[8]
Does tirzepatide reduce the severity of obstructive sleep apnea in adults with obesity?
- Who was in it
- 469 adults with moderate-to-severe sleep apnea and obesity, without type 2 diabetes, in two trials (with and without CPAP)
- What they got
- Tirzepatide at the highest tolerated dose (10 or 15 mg) once a week
- Compared with
- Placebo
- How long
- 52 weeks
- What happened
- Breathing interruptions per hour (AHI) fell by 25.3 vs 5.3 (trial 1) and 29.3 vs 5.5 (trial 2) on tirzepatide vs placebo.
- Limits
- People with diabetes were excluded
- 52 weeks
- The effect may be largely through weight loss
- Funded by
- Eli Lilly
Summary by Joshua Nichvolodoff, from the published paper — not written by the study's authors. Clinical review: not yet reviewed by a clinician.
Study: SURPASS-CVOT[9]
Is tirzepatide at least as good as dulaglutide at preventing heart attacks, strokes and cardiovascular deaths in type 2 diabetes with heart disease?
- Who was in it
- 13,299 adults with type 2 diabetes and atherosclerotic cardiovascular disease
- What they got
- Tirzepatide up to 15 mg once a week
- Compared with
- Dulaglutide 1.5 mg once a week (another GLP-1 medicine)
- How long
- Event-driven, multi-year
- What happened
- Heart attack, stroke or cardiovascular death: 12.2% on tirzepatide vs 13.1% on dulaglutide.
- Relative effect
- Hazard ratio 0.92 (95.3% CI 0.83–1.01): non-inferior; superiority not shown
- Limits
- No placebo group — compared with another GLP-1 medicine
- Superiority was not shown
- Funded by
- Eli Lilly
Summary by Joshua Nichvolodoff, from the published paper — not written by the study's authors. Clinical review: not yet reviewed by a clinician.
Brand pages
General information, not medical advice. Which product and dose is right for you is a decision for you and your prescriber. Light Years earns nothing from any product named here.
Log each dose and see when the next one is due, on your device. Open my tracker or browse the other guides.
Sources
- MOUNJARO (tirzepatide) injection — prescribing information. U.S. Food and Drug Administration (FDALabel). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/d2d7da5d-ad07-4228-955f-cf7e355c8cc0/spl-doc. Accessed November 2, 2026. Back to the text
- ZEPBOUND (tirzepatide) injection — prescribing information. U.S. Food and Drug Administration (FDALabel), August 2026. https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/487cd7e7-434c-4925-99fa-aa80b1cc776b/spl-doc. Accessed November 2, 2026. Back to the text
- Mounjaro / Mounjaro KwikPen (tirzepatide injection) product monograph. Health Canada Drug Product Database / Eli Lilly Canada, June 23, 2026. https://pdf.hres.ca/dpd_pm/00085122.PDF. Accessed November 2, 2026. Back to the text
- Zepbound (tirzepatide injection) KwikPen product monograph. Health Canada Drug Product Database / Eli Lilly Canada, April 2, 2026. https://pdf.hres.ca/dpd_pm/00084150.PDF. Accessed November 2, 2026. Back to the text
- Health Canada approves Zepbound as the first-ever obstructive sleep apnea medication (Eli Lilly Canada release). Eli Lilly Canada (via BioSpace), June 16, 2026. https://www.biospace.com/press-releases/health-canada-approves-zepbound-as-the-first-ever-obstructive-sleep-apnea-medication-in-canada-for-adults-living-with-obesity. Accessed November 2, 2026. Back to the text
- Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). New England Journal of Medicine, July 21, 2022. https://pubmed.ncbi.nlm.nih.gov/35658024/ · DOI 10.1056/NEJMoa2206038 · PMID 35658024. Accessed November 2, 2026. Back to the text
- Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes (SURPASS-2). New England Journal of Medicine, August 5, 2021. https://pubmed.ncbi.nlm.nih.gov/34170647/ · DOI 10.1056/NEJMoa2107519 · PMID 34170647. Accessed November 2, 2026. Back to the text
- Tirzepatide for the treatment of obstructive sleep apnea and obesity (SURMOUNT-OSA). New England Journal of Medicine, October 3, 2024. https://pubmed.ncbi.nlm.nih.gov/38912654/ · DOI 10.1056/NEJMoa2404881 · PMID 38912654. Accessed November 2, 2026. Back to the text
- Cardiovascular outcomes with tirzepatide versus dulaglutide in type 2 diabetes (SURPASS-CVOT). New England Journal of Medicine, December 18, 2025. https://pubmed.ncbi.nlm.nih.gov/41406444/ · DOI 10.1056/NEJMoa2505928 · PMID 41406444. Accessed November 2, 2026. Back to the text
Figures marked “as reported” are historical: they show what the source said on that date, not today's price or rule.
Changes to this page
- — First published.
Substantive corrections are also logged at corrections.