Guides / Comparing and switching

Ozempic vs Mounjaro

Both are weekly injections, but the medicine inside is different. Each also has a sister brand for weight loss, Wegovy and Zepbound, compared here too.

By PeptideTracker editorial team · Updated November 8, 2026 · 11 sources

[00] Short answer

  1. Ozempic is semaglutide, which acts on the GLP-1 receptor. Mounjaro is tirzepatide, which acts on both the GIP and GLP-1 receptors1,3.
  2. Both are once-weekly injections. Ozempic doses run from 0.25 mg to 2 mg; Mounjaro from 2.5 mg to 15 mg1,3.
  3. In the US both are for type 2 diabetes. The weight-management versions are Wegovy (semaglutide) and Zepbound (tirzepatide)1–4.
  4. In the SURMOUNT-5 trial, average weight loss at 72 weeks was 20.2% with tirzepatide and 13.7% with semaglutide9.

Ozempic vs Mounjaro: what's the difference?

The main difference is the medicine inside. Ozempic contains semaglutide, a GLP-1 receptor agonist. Mounjaro contains tirzepatide, which acts on both the GIP and GLP-1 receptors1,3. Both are injected under the skin once a week, and in the US both are approved for type 2 diabetes1,3.

Ozempic vs Mounjaro, from the US prescribing information
OzempicMounjaro
Active ingredientSemaglutide1Tirzepatide3
How it worksGLP-1 receptor agonist1GIP receptor and GLP-1 receptor agonist3
US approved usesType 2 diabetes in adults; lowering the risk of heart attack, stroke and heart death in adults with type 2 diabetes and heart disease; lowering the risk of kidney function decline, kidney failure and heart death in adults with type 2 diabetes and chronic kidney disease1Type 2 diabetes in adults and children aged 10 and over; lowering the risk of heart attack, stroke and heart death in adults with type 2 diabetes at high risk3
How oftenOnce a week1Once a week3
DosesStart 0.25 mg, then 0.5 mg, 1 mg or 2 mg (maximum)1Start 2.5 mg, up in 2.5 mg steps to 15 mg (maximum in adults)3
Half-lifeAbout 1 week1About 5 days3
Most common side effectsNausea, vomiting, diarrhea, stomach pain, constipation1Nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion, stomach pain3
Boxed warningThyroid C-cell tumors (seen in rodents)1Thyroid C-cell tumors (seen in rodents)3

Wegovy vs Zepbound: the weight-loss versions

Wegovy is semaglutide and Zepbound is tirzepatide, the same medicines as Ozempic and Mounjaro, approved in the US for weight reduction. Wegovy goes up to 2.4 mg a week (7.2 mg for some adults), and Zepbound up to 15 mg a week2,4.

Wegovy vs Zepbound, from the US prescribing information
WegovyZepbound
Active ingredientSemaglutide2Tirzepatide4
US approved usesWeight reduction in adults and children 12 and over; lowering heart risks in adults with heart disease and obesity or overweight; a type of fatty liver disease (MASH) with liver scarring2Weight reduction in adults; moderate to severe obstructive sleep apnea in adults with obesity4
How takenWeekly injection, or a daily tablet (25 mg maintenance)2Weekly injection4
Injection dosesStart 0.25 mg, step up every 4 weeks to 1.7 mg or 2.4 mg; up to 7.2 mg for weight reduction in adults2Start 2.5 mg for 4 weeks, then 5 mg, 10 mg or 15 mg4
Half-lifeAbout 1 week2About 5 to 6 days4
Nausea in the main label table44% on 2.4 mg vs 16% on placebo225% to 29% on 5–15 mg vs 8% on placebo4

Ozempic and Wegovy contain the same medicine but are separate products with different doses and approved uses. The same is true of Mounjaro and Zepbound1–4.

Which causes more weight loss, semaglutide or tirzepatide?

Tirzepatide led to more weight loss in SURMOUNT-5, the one head-to-head trial: an average of 20.2% of body weight vs 13.7% on semaglutide after 72 weeks. The trial had 751 adults with obesity and without type 2 diabetes9. People took the highest dose they tolerated: 10 mg or 15 mg of tirzepatide, or 1.7 mg or 2.4 mg of semaglutide9.

Average weight change in the main obesity trials (adults without diabetes)
TrialMedicine and doseLengthAverage weight changePlacebo or comparison
STEP 17Semaglutide 2.4 mg weekly68 weeks−14.9%Placebo −2.4%
SURMOUNT-18Tirzepatide 5 mg / 10 mg / 15 mg weekly72 weeks−15.0% / −19.5% / −20.9%Placebo −3.1%
SURMOUNT-59Tirzepatide 10–15 mg vs semaglutide 1.7–2.4 mg72 weeks−20.2% vs −13.7%Head to head, no placebo

These trials used the weight-management doses (Wegovy and Zepbound strengths). Ozempic's maximum dose is 2 mg, so its diabetes doses weren't what these trials tested.

  • STEP 1 enrolled 1,961 adults and SURMOUNT-1 enrolled 2,539. All had obesity, or overweight plus a weight-related condition, and none had diabetes7–8.
  • SURMOUNT-1 and SURMOUNT-5 were funded by Eli Lilly, which makes tirzepatide. STEP 1 was funded by Novo Nordisk, which makes semaglutide7–9.
  • These are averages. They don't tell you how much one person will lose.

Ozempic vs Mounjaro side effects

Both labels list nausea, diarrhea, vomiting and constipation among the most common side effects. In the diabetes trials, nausea was reported by 15.8% to 20.3% of people on Ozempic 0.5 mg to 1 mg, and 12% to 18% on Mounjaro 5 mg to 15 mg1,3.

  • Both labels say most nausea, vomiting and diarrhea happened while the dose was being increased1,3.
  • Both carry the same boxed warning about thyroid C-cell tumors seen in rodents, and both list pancreatitis, gallbladder disease and severe stomach side effects as warnings1,3.
  • Each label says side-effect rates from one drug's trials "cannot be directly compared" to rates from another drug's trials1,3.

For the rates by dose and how long the side effects tend to last, see our GLP-1 side effects guide.

Ozempic vs Mounjaro pens, vials and missed-dose rules

Ozempic comes in multi-dose pens and single-dose prefilled syringes. Mounjaro comes in single-dose pens, single-dose vials, and 4-dose multi-dose vials and KwikPens1,3. Their missed-dose and day-change rules also differ.

Supply and timing rules from the US prescribing information
OzempicMounjaro
How suppliedMulti-dose pens: 2 mg/3 mL (0.25 mg and 0.5 mg doses), 4 mg/3 mL (1 mg), 8 mg/3 mL (2 mg); single-dose syringes of 0.25 mg, 0.5 mg and 1 mg1Single-dose pens or vials (2.5 mg to 15 mg in 0.5 mL); multi-dose vials and KwikPens holding 4 doses3
Missed doseTake within 5 days, otherwise skip1Take within 4 days (96 hours), otherwise skip3
Changing your injection dayAt least 2 days (more than 48 hours) between doses1At least 3 days (72 hours) between doses3

Our missed-dose guide has a day-by-day table for each weekly medicine.

Ozempic vs Mounjaro in the UK

In the UK, Ozempic is licensed only for type 2 diabetes, while Mounjaro is licensed for both type 2 diabetes and weight management5–6. So in the UK, tirzepatide for weight management is prescribed as Mounjaro, and semaglutide for weight management as Wegovy6,10.

  • UK Mounjaro: 2.5 mg for 4 weeks, then 5 mg, with 2.5 mg steps after at least 4 weeks, up to 15 mg6.
  • UK Wegovy: 0.25 mg rising over 16 weeks to 2.4 mg, with 7.2 mg possible for adults with obesity after at least 4 weeks on 2.4 mg11.
  • UK Ozempic: 0.25 mg, then 0.5 mg, 1 mg or 2 mg; weekly doses above 2 mg are not recommended5.

Questions

Is Mounjaro stronger than Ozempic?

They are different medicines, so their mg doses can't be compared. In the SURMOUNT-5 trial of the weight-management doses, tirzepatide led to more average weight loss than semaglutide: 20.2% vs 13.7% after 72 weeks.

Is Ozempic the same as Wegovy?

Both contain semaglutide, but they are separate products. In the US, Ozempic is approved for type 2 diabetes with a maximum of 2 mg a week, and Wegovy for weight reduction and other uses, usually at 2.4 mg a week.

Is Mounjaro the same as Zepbound?

Both contain tirzepatide with the same 2.5 mg to 15 mg dose range. In the US, Mounjaro is approved for type 2 diabetes and Zepbound for weight reduction and obstructive sleep apnea with obesity. In the UK, Mounjaro covers both diabetes and weight management.

Which has more side effects, Ozempic or Mounjaro?

Both most often cause nausea, diarrhea, vomiting and constipation. The labels say rates from one drug's trials can't be directly compared with another's.

Which stays in the body longer?

Semaglutide has a half-life of about 1 week. Tirzepatide's is about 5 days, or 5 to 6 days in people with obesity according to the Zepbound label.

Sources

Checked against Ozempic, Wegovy, Mounjaro and Zepbound US prescribing information (2026), the UK SmPCs for Ozempic, Wegovy and Mounjaro, and the STEP 1, SURMOUNT-1 and SURMOUNT-5 trials (NEJM). How we check

  1. 1Ozempic (semaglutide) injection, US prescribing information, sections 1, 2.1, 2.2, 3, 5, 6.1, 12.1 and 12.3. Novo Nordisk, revised 05/2026; Table 1
  2. 2Wegovy (semaglutide) injection and tablets, US prescribing information, sections 1, 2.2, 2.3, 6.1 and 12.3. Novo Nordisk, revised 06/2026; Table 3
  3. 3Mounjaro (tirzepatide) US prescribing information, sections 1, 2.1, 3, 5, 6.1, 12.1 and 12.3. Eli Lilly, revised 08/2026; Table 1
  4. 4Zepbound (tirzepatide) US prescribing information, sections 1, 2.1, 2.2, 6.1 and 12.3. Eli Lilly, revised 08/2026; Table 1
  5. 5Ozempic 0.25 mg solution for injection, UK SmPC, sections 4.1 and 4.2. eMC, updated 28 Jul 2026
  6. 6Mounjaro KwikPen solution for injection, UK SmPC, sections 4.1 and 4.2. eMC, updated 8 Sep 2026
  7. 7Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med 2021;384:989-1002. PubMed 33567185
  8. 8Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med 2022;387:205-216. PubMed 35658024
  9. 9Aronne LJ, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5). N Engl J Med 2025;393:26-36. PubMed 40353578
  10. 10Wegovy FlexTouch solution for injection, UK SmPC, section 4.1. eMC, updated 22 Sep 2026
  11. 11Wegovy 7.2 mg solution for injection in pre-filled pen, UK SmPC, section 4.2. eMC, updated 1 Oct 2026

This guide explains what labels and published studies say. It isn't medical advice and doesn't replace your prescriber or pharmacist.

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