Tirzepatide and Semaglutide: Dose Escalation and Side-Effect Profile
How tirzepatide and semaglutide 2.4mg differ on dose escalation schedule and side-effect profile, and what to raise with a UK-registered prescriber. Patient information, no prescription-medicine prices.
Quick answer
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- Use NHS eligibility tools separately from private price comparison.
Important information for UK consumers. Mounjaro (tirzepatide) and Wegovy (semaglutide 2.4mg) are prescription-only medicines (POMs) in the UK. UK regulations restrict the advertising of prescription medicines to the public, so this article is a clinical comparison for patient information — it is not an advertisement, not an offer of sale, and not medical advice. This article does not display UK prices.
In short
- Mounjaro contains tirzepatide (a dual GIP/GLP-1 receptor agonist). Wegovy contains semaglutide 2.4mg (a GLP-1 receptor agonist). They use different mechanisms.
- The pivotal trials were SURMOUNT-1 (tirzepatide) and STEP-1 (semaglutide 2.4mg). Their weight-loss results are population averages, and individual response varies.
- Both are once-weekly subcutaneous injections with stepped dose escalation under prescriber guidance. Side-effect profiles are similar and gastrointestinal-dominant.
- Suitability is a clinical decision for a UK-registered prescriber following an assessment. This article does not display UK prices.
Mechanism
| Aspect | Mounjaro (tirzepatide) | Wegovy (semaglutide 2.4mg) |
|---|---|---|
| Class | Dual GIP / GLP-1 receptor agonist | GLP-1 receptor agonist |
| Manufacturer | Eli Lilly | Novo Nordisk |
| Administration | Once-weekly subcutaneous injection (KwikPen) | Once-weekly subcutaneous injection (FlexTouch pen) |
| UK indication | Weight management in eligible adults; separately licensed for type 2 diabetes | Weight management in eligible adults |
| NICE technology appraisal | TA1026 | TA875 |
Dose escalation
Both medicines use a stepped dose-escalation schedule under prescriber guidance, designed to manage gastrointestinal tolerability:
| Step | Mounjaro | Wegovy |
|---|---|---|
| Start | 2.5mg weekly | 0.25mg weekly |
| Increments | 5mg → 7.5mg → 10mg → 12.5mg → 15mg | 0.5mg → 1mg → 1.7mg → 2.4mg |
| Typical escalation | Several months | Around 16 weeks |
| Maintenance | Up to 15mg weekly (clinical decision) | 2.4mg weekly |
Side-effect profile
Both medicines share a broadly similar side-effect profile, dominated by gastrointestinal effects during dose escalation. The MHRA Drug Safety Update on GLP-1 receptor agonists is the authoritative UK pharmacovigilance source.
| Effect | Mounjaro | Wegovy |
|---|---|---|
| Nausea | Common, particularly at escalation | Common, particularly at escalation |
| Vomiting | Common | Common |
| Diarrhoea | Common | Common |
| Constipation | Common | Common |
| Injection-site reactions | Common | Common |
| Pancreatitis (rare) | Reported | Reported |
| Gallbladder events | Reported | Reported |
See the MHRA Yellow Card side-effects data page for UK real-world reporting summaries.
Healthcare data note
Sources, review and limits
Main sources
- NICE TA1026 — Tirzepatide for managing overweight and obesity
- NICE TA875 — Semaglutide for managing overweight and obesity
- MHRA Drug Safety Update on GLP-1 receptor agonists
- Manufacturer Summaries of Product Characteristics (SmPCs) for Mounjaro and Wegovy
- Published pivotal trial outputs: SURMOUNT-1 (tirzepatide) and STEP-1 (semaglutide 2.4mg)
Methodology: This article is a clinical comparison of the two medicines for UK patient information. It describes mechanism, dose escalation, side-effect profile and NHS access framework. It does not display UK private prices, recommend either medicine, or replace prescriber assessment. Trial endpoints quoted are population averages from pivotal trials; individual response varies. The UK Human Medicines Regulations 2012 prohibit advertising prescription-only medicines to the public, so price comparisons are not included.
NHS access
Both medicines are recommended by NICE for weight management in eligible adults under separate technology appraisals. NHS rollout is staged by cohort and decided by NHS England commissioning policy. Use the NHS eligibility checker.
What to discuss with a UK prescriber
- Which medicine is more appropriate for your circumstances, based on indication and clinical profile.
- The dose escalation schedule and tolerability monitoring approach.
- Common and serious side effects, and what to do if they occur.
- Whether NHS-funded treatment is realistic, and the practical timing.
- The follow-up review schedule and ongoing monitoring requirements.
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Important context
Healthcare prices can change without notice and may exclude consultation fees, medication, diagnostics, anaesthetic, facility fees, follow-up care or add-ons. TreatCompare summarises published or compiled pricing for comparison and planning only. Always verify the current total directly before paying.
- Source type
- TreatCompare compiled research
- Primary source
- Provider-published information and TreatCompare research
- Reporting period
- 2026-05-12
- Last updated
- 2026-05-12
- Figure type
- Mixed sources
- Use
- Research and comparison only
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Frequently asked questions
What is the difference between Mounjaro and Wegovy?
Both are once-weekly subcutaneous injections for weight management in adults who meet the indication. Mounjaro contains tirzepatide and is a dual GIP/GLP-1 receptor agonist (Eli Lilly). Wegovy contains semaglutide 2.4mg and is a GLP-1 receptor agonist (Novo Nordisk). They have different mechanisms, dose schedules and side-effect profiles. Suitability is a clinical decision for a UK-registered prescriber.
Which is more effective for weight management?
Pivotal trial data (SURMOUNT-1 for tirzepatide, STEP-1 for semaglutide 2.4mg) reported mean percentage body-weight reduction in the order of around 21% for tirzepatide 15mg and around 15% for semaglutide 2.4mg over 68–72 weeks. Trial endpoints are population averages; individual response varies by dose, adherence and other factors. Discuss the most relevant evidence with a UK-registered prescriber.
Why does this comparison not show prices?
Mounjaro and Wegovy are prescription-only medicines (POMs) in the UK. UK Human Medicines Regulations 2012 prohibit advertising POMs to the public, including price comparisons. TreatCompare therefore does not display UK Mounjaro or Wegovy prices.
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