Guides / Comparing and switching

Switching from tirzepatide to semaglutide

Moving from Mounjaro or Zepbound to Wegovy or Ozempic usually means starting semaglutide from the bottom. The labels and pharmacy guidance below are a starting point for the talk with your prescriber.

By PeptideTracker editorial team · Updated November 8, 2026 · 10 sources

[00] Short answer

  1. There is no validated dose conversion between tirzepatide and semaglutide1. No label gives one, and no tirzepatide dose "equals" a semaglutide dose.
  2. The Wegovy and Ozempic labels start semaglutide at 0.25 mg once weekly for 4 weeks2–3. Pharmacy guidance says to start there whatever tirzepatide dose you were on1.
  3. Two timing options are described: start semaglutide on the day your next tirzepatide dose was due, or wait 1 to 2 weeks1.
  4. In the UK there is no NICE or MHRA guidance on how to make this switch1. The MHRA says to get advice from a healthcare professional before switching7.

Is there a tirzepatide to semaglutide dose conversion?

No. There is no validated dose equivalence between tirzepatide and semaglutide, because they act on different receptors1. Tirzepatide acts on the GIP and GLP-1 receptors, and semaglutide on the GLP-1 receptor only2,4.

The Wegovy and Ozempic labels don't give a starting dose for people coming from tirzepatide. The only switching instructions on the Wegovy label are between Wegovy injections and Wegovy tablets2–3. Charts online that pair, say, 10 mg of tirzepatide with a particular semaglutide dose don't come from the labels or from a validated source.

What dose of semaglutide do you start on after tirzepatide?

The labels start everyone on 0.25 mg of semaglutide once weekly for 4 weeks. That applies to Wegovy and Ozempic alike, and neither has a different start for people who have taken tirzepatide2–3.

The Pharmaceutical Journal's switching guide says the safest approach is to restart semaglutide at 0.25 mg weekly. Its example is someone on tirzepatide 10 mg starting semaglutide 0.25 mg once weekly for four weeks1.

Semaglutide schedules after a switch, from the labels
WeeksWegovy injection (US and UK)Ozempic (US)
1 to 40.25 mg0.25 mg
5 to 80.5 mg0.5 mg
9 to 121 mg0.5 mg, or 1 mg if more blood sugar control is needed
13 to 161.7 mg1 mg, or 2 mg after at least 4 weeks on 1 mg
17 onward2.4 mg maintenance; 7.2 mg possible for weight after 4+ weeks on 2.4 mgUp to 2 mg maximum

Wegovy: US Table 1 and UK SmPC Table 22,6. Ozempic: US section 2.23. In the UK, 7.2 mg is only for adults with obesity (BMI 30 or more)6.

So reaching 2.4 mg of Wegovy takes 16 weeks of step-ups2. If a step isn't tolerated, the US label says to consider waiting 4 more weeks, and the UK SmPC says to consider delaying or going back to the previous dose until symptoms improve2,6.

[Tool]Plan your semaglutide step-ups as datesStarts at 0.25 mg, from the label schedule

How long after your last tirzepatide dose do you start semaglutide?

The labels don't set a gap. They say not to use the two together: Wegovy isn't recommended with any other GLP-1 medicine, and Zepbound isn't recommended with any GLP-1 medicine2,4. The Pharmaceutical Journal guide describes two ways to time it1:

  • Same-day switch: start semaglutide on the day your next tirzepatide dose would have been due. The guide suggests this for stable people at low risk.
  • Washout: wait 1 to 2 weeks before the first semaglutide dose. The guide favors this when side effects are significant.

Tirzepatide has a half-life of about 5 days, or 5 to 6 days in people with obesity4–5. That means levels fall by about half every 5 days or so after your last dose.

[Tool]See how tirzepatide levels fall after the last doseUses the half-life in the label

What changes when you move from tirzepatide to semaglutide?

You go back to step-ups, a different missed-dose rule and a longer gap before pregnancy. Semaglutide stays in the body longer, with a half-life of about 1 week against about 5 days for tirzepatide2,5.

Tirzepatide vs semaglutide: rules that change with a switch
Tirzepatide (Mounjaro, Zepbound)Semaglutide (Wegovy injection)
Starting dose2.5 mg weekly4–50.25 mg weekly2
Highest dose15 mg4–52.4 mg, or 7.2 mg for weight in adults2
Half-lifeAbout 5 days5About 1 week2
Missed dose (US)Within 4 days4Take it if the next dose is more than 2 days away2
Missed dose (UK)Within 4 days8Within 5 days6
Stop before a planned pregnancy (MHRA)At least 1 month7At least 2 months7

Starting again at a low dose means going back through the step-ups, which is when stomach side effects are most likely. The Wegovy label says to follow the step-ups to reduce that risk2. In its weight trials, nausea was reported by 44% on 2.4 mg vs 16% on placebo2.

In SURMOUNT-5, average weight loss at 72 weeks was 13.7% on semaglutide and 20.2% on tirzepatide9. People in that trial stayed on one medicine. It didn't test switching, so it can't say what happens to weight after a switch. See Wegovy vs Zepbound for the full results.

Switching from Mounjaro to Wegovy in the UK

In the UK there is no NICE or MHRA guidance that sets out how to switch from tirzepatide to semaglutide. The Pharmaceutical Journal guide says so, and points to each medicine's SmPC instead1. The MHRA tells patients to consult a healthcare professional before switching, because switching without advice "may increase the risk of experiencing side effects or make the treatment less effective"7.

Cost is one reason people switch. The Pharmaceutical Journal guide lists cost pressures alongside side effects, preference and formulary decisions, and mentions the Mounjaro price rise1. Lilly raised the UK list price from 1 September 2025: the NHS price per pen went from £92 to £133 for 2.5 mg and from £122 to £330 for 15 mg10.

Mounjaro KwikPen UK list price per pen, before and from September 2025 (Community Pharmacy England)
StrengthBeforeFrom September 2025
2.5 mg£92£133
5 mg£92£180
7.5 mg£107£255
10 mg£107£255
12.5 mg£122£330
15 mg£122£330

NHS list and reimbursement prices10. Private pharmacy prices vary and aren't covered here.

  • The same guide says switching "should not be driven by price alone"1.
  • Wegovy in the UK steps up over 16 weeks to 2.4 mg6. Its SmPC says to review whether to continue if you haven't lost at least 5% of your starting weight after 6 months6.
  • The UK Wegovy pen is a 4-dose FlexTouch, a different device from the Mounjaro KwikPen6,8.

Going the other way? See switching from semaglutide to tirzepatide. Check with your prescriber or pharmacist before you change anything.

Questions

What dose of Wegovy is equal to Mounjaro 10 mg?

No dose is validated as equal. Tirzepatide and semaglutide act on different receptors. The Wegovy label starts everyone at 0.25 mg weekly for 4 weeks, and pharmacy guidance gives the example of someone on tirzepatide 10 mg starting semaglutide at 0.25 mg.

Can I start Wegovy at 2.4 mg if I was on Mounjaro 15 mg?

The labels don't give that option. Wegovy starts at 0.25 mg and steps up every 4 weeks to reach 2.4 mg at week 17. Any other plan is your prescriber's decision.

Do I need a gap between my last Mounjaro and first Wegovy?

The labels don't set one, but they say not to use the two together. Pharmacy guidance describes starting on the day your next tirzepatide dose was due, or waiting 1 to 2 weeks, which it favors if side effects are significant.

Will I get side effects again when I switch?

Possibly. You go back through the semaglutide step-ups, which is when stomach side effects are most likely. In the Wegovy weight trials, nausea was reported by 44% of people on 2.4 mg.

Is there NHS or MHRA guidance on switching from Mounjaro to Wegovy?

Not on how to do it. The Pharmaceutical Journal reports there is no NICE or MHRA guidance that specifies how to switch. The MHRA says to get advice from a healthcare professional before switching between GLP-1 medicines.

How much did the UK Mounjaro price go up?

Lilly raised the UK list price from 1 September 2025. The NHS price per pen went from £92 to £133 for 2.5 mg and from £122 to £330 for 12.5 mg and 15 mg.

Sources

Checked against Wegovy, Ozempic, Zepbound and Mounjaro US prescribing information (2026), the UK Wegovy SmPC, the MHRA's GLP-1 guidance (February 2026), the Pharmaceutical Journal switching article (July 2026) and Community Pharmacy England's September 2025 Mounjaro price notice. How we check

  1. 1Shahid S. Switching between weight-loss medications. The Pharmaceutical Journal. published 24 July 2026, updated 27 July 2026; the author discloses work as a clinical trainer for Eli Lilly
  2. 2Wegovy (semaglutide) injection and tablets, US prescribing information, sections 1, 2.2, 2.4, 2.5, 6.1 and 12.3. Novo Nordisk, revised 06/2026
  3. 3Ozempic (semaglutide) injection, US prescribing information, section 2.2. Novo Nordisk, revised 05/2026
  4. 4Zepbound (tirzepatide) US prescribing information, sections 1, 2.1, 2.3 and 12.3. Eli Lilly, revised 08/2026
  5. 5Mounjaro (tirzepatide) US prescribing information, sections 2.1 and 12.3. Eli Lilly, revised 08/2026
  6. 6Wegovy FlexTouch solution for injection in pre-filled pen, UK SmPC, sections 4.2 and 6.5. eMC, updated 22 Sep 2026
  7. 7MHRA: GLP-1 medicines for weight loss and diabetes: what you need to know (GOV.UK). updated 5 Feb 2026; sections on switching and pregnancy
  8. 8Mounjaro KwikPen solution for injection in pre-filled pen, UK SmPC, sections 2 and 4.2. eMC, updated 8 Sep 2026
  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. 10Community Pharmacy England: Mounjaro reimbursement prices redetermined for September 2025. published 1 Sep 2025

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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