What Dose of Mounjaro Do I Start On After Wegovy? Your UK Switching Guide
⚡ Quick Summary
- No direct conversion exists. Mounjaro and Wegovy contain different active ingredients with different mechanisms of action.
- Most patients start on 2.5mg or 5mg. Your Wegovy dose and side effect tolerance determine the starting point.
- Titration takes 4-8 weeks minimum. You'll increase doses gradually until finding your effective maintenance dose.
- Higher Wegovy dose ≠ higher Mounjaro start. Even patients on 2.4mg Wegovy often start on 5mg Mounjaro.
- Individual assessment matters. Generic conversion charts don't account for your personal response and tolerance.
📋 Quick Navigation
- → Why There's No Direct Dose Conversion
- → Recommended Starting Doses
- → Understanding Mounjaro's Titration Schedule
- → Why You Can't Skip Straight to High Dose
- → What If You Had Side Effects on Wegovy?
- → The First Few Weeks: What to Expect
- → How G-1 Nutrition Determines Your Starting Dose
- → Common Dose-Related Questions
- → Frequently Asked Questions
What Dose of Mounjaro Do I Start On After Wegovy? Your UK Switching Guide
You've made the decision to switch from Wegovy to Mounjaro. Your prescription is sorted, you've waited your 7 days, and now you're staring at your new pen wondering: what dose am I supposed to start on?
It's a fair question. You were on 2.4mg of Wegovy, the highest dose available. Does that mean you can jump straight onto a high Mounjaro dose too?
After all, you've been on weight loss injections for months. Your body should be used to them by now. Not quite. Mounjaro and Wegovy are different medications with different active ingredients and different strengths. There's no direct "mg for mg" conversion, and getting your starting dose wrong can mean unnecessary side effects or, worse, wasted time and money on a dose that doesn't work properly. This guide explains exactly what dose you should start on based on your current Wegovy dose, why the conversion isn't straightforward, and how G-1 Nutrition helps you get it right from day one.
Why There's No Direct Dose Conversion
If you're expecting a simple chart showing "Wegovy 2.4mg = Mounjaro 10mg" or something similar, you're going to be disappointed. These medications work differently, which makes direct conversion impossible.
Wegovy contains semaglutide, a GLP-1 receptor agonist. It targets one type of hormone receptor to reduce your appetite and help you feel fuller. Mounjaro contains tirzepatide, a dual GIP and GLP-1 receptor agonist. It targets two types of hormone receptors, which is partly why clinical trials show higher average weight loss with Mounjaro.
Because tirzepatide hits two pathways instead of one, it tends to have a more potent effect. A 5mg dose of Mounjaro isn't the same as a 5mg dose of anything else. The dosing schedules were developed separately based on how each medication performs in clinical trials, not based on any equivalence between them.
This is why you can't just look at the numbers and guess. A proper clinical assessment considers your Wegovy history, side effect tolerance, and individual response to determine the safest and most effective starting point.
For more on how the switching process works and what to expect from start to finish, see our complete guide to swapping Mounjaro providers in the UK.
Recommended Starting Doses Based on Your Wegovy Dose
While there's no perfect conversion, UK providers have developed general guidance based on clinical experience. Here's what most prescribers recommend:
📋 Starting Dose Guidelines:
| Your Wegovy Dose | Recommended Mounjaro Start | Notes |
|---|---|---|
| 0.25mg - 0.5mg | 2.5mg (lowest dose) | Standard starting point |
| 1mg | 2.5mg (lowest dose) | May move to 5mg after 4 weeks if tolerated |
| 1.7mg | 5mg | Skip titration dose if well tolerated |
| 2.4mg (highest) | 5mg | May start on 2.5mg if had side effects |
Important: These are general guidelines. Your actual starting dose should be determined by a qualified prescriber who reviews your complete medical history, side effect profile, and weight loss progress. Some patients on high Wegovy doses still need to start Mounjaro at 2.5mg, particularly if they experienced significant side effects.
Understanding Mounjaro's Titration Schedule
Regardless of where you start, Mounjaro follows a specific titration schedule. The recommended approach from Eli Lilly (the manufacturer) is to increase your dose by 2.5mg every four weeks until you reach a maintenance dose that works for you.
The available doses are: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg, and 15mg. The 2.5mg dose is considered a "starting" dose rather than a maintenance dose. Most patients find their effective maintenance dose somewhere between 5mg and 15mg.
Here's what a typical titration might look like if you start on 2.5mg:
- Weeks 1-4: 2.5mg (starting dose)
- Weeks 5-8: 5mg (first maintenance dose)
- Weeks 9-12: 7.5mg (if needed)
- Weeks 13-16: 10mg (if needed)
- Weeks 17-20: 12.5mg (if needed)
- Weeks 21+: 15mg (maximum dose, if needed)
The key phrase there is "if needed." Not everyone requires the maximum dose. Some patients achieve excellent results on 5mg or 7.5mg and stay there. Others need to work up to higher doses before seeing significant appetite suppression.
Your prescriber should monitor your progress and only increase your dose when clinically appropriate.
Why You Can't Skip Straight to High Dose
It's tempting to think that because you've been on Wegovy for months, your body is already "trained" for GLP-1 medications. Some patients ask whether they can skip the titration process entirely and start on 10mg or even 15mg Mounjaro.
The short answer is no, and here's why.
⚠️ Reasons You Can't Skip Titration:
- Different medication: Even though both work on GLP-1 receptors, tirzepatide has additional effects through the GIP pathway. Your body hasn't been exposed to GIP agonism before, so it needs time to adjust to this new mechanism.
- Different potency: Clinical trials suggest Mounjaro may be more potent milligram-for-milligram than Wegovy for appetite suppression. Starting too high risks severe gastrointestinal side effects like nausea, vomiting, and diarrhoea that could put you off the medication entirely.
- Evidence-based titration: Dose escalation was specifically designed to reduce side effects. The SURPASS and SURMOUNT clinical trials that led to Mounjaro's approval used gradual titration specifically because it resulted in better tolerability.
- Rushing doesn't help: Patients who skip titration often end up having to drop back down due to intolerable side effects, actually slowing their progress compared to those who increased gradually.
What If You Had Side Effects on Wegovy?
If you struggled with nausea, vomiting, constipation, or other side effects while on Wegovy, this significantly affects your Mounjaro starting dose recommendation.
Most prescribers will recommend starting you on 2.5mg regardless of how high your Wegovy dose was. The reasoning is straightforward: if your body was sensitive to semaglutide, it may also be sensitive to tirzepatide. Starting at the lowest dose gives your system the gentlest possible introduction to the new medication.
✅ Important Considerations:
- This isn't a step backwards. Some patients who struggled with Wegovy side effects find they tolerate Mounjaro much better, and vice versa.
- The medications affect people differently despite working through similar pathways.
- There's no way to know how you'll respond until you try it, so caution makes sense.
- If you tolerate 2.5mg well with minimal side effects, your prescriber may recommend moving to 5mg after four weeks as normal.
From there, titration continues based on your individual response.
The First Few Weeks: What to Expect
Starting on a lower Mounjaro dose than your Wegovy dose can feel like going backwards. You might notice your appetite returning slightly, particularly if you were on 2.4mg Wegovy and are now starting on 5mg or even 2.5mg Mounjaro.
📅 What's Normal During the First Few Weeks:
- This is normal and temporary. Within the first week or two, the new medication begins to take effect.
- Gradual improvement: As you titrate up to higher doses, appetite suppression typically increases.
- Fewer side effects: Many patients experience fewer problems when starting Mounjaro than they did when starting Wegovy, likely because your digestive system has already adapted to GLP-1 effects.
- Mild symptoms possible: Don't be surprised if mild nausea or digestive changes occur, particularly around dose increases.
- Weight may pause briefly: Weight loss may pause briefly during the transition as your body adjusts to the new medication.
Don't panic if the scales stall for a week or two. Once you reach an effective maintenance dose, weight loss typically resumes.
How G-1 Nutrition Determines Your Starting Dose
At G-1 Nutrition, we don't use a one-size-fits-all approach to switching patients from Wegovy to Mounjaro. Our GPhC-registered pharmacist reviews each case individually to determine the safest and most effective starting dose.
🔬 Our Personalised Assessment Includes:
- Your complete Wegovy history: Current dose, how long you've been on it, and any side effects experienced
- Weight loss progress: How well Wegovy has worked for you and whether you've plateaued
- Side effect tolerance: How you handled dose increases and any digestive issues
- Individual health profile: Your overall health status and any relevant medical conditions
- Personal goals: What you're hoping to achieve with Mounjaro
This personalised approach means you're not guessing at your dose or relying on generic advice from the internet. You get clinical guidance based on your specific circumstances, with ongoing support as you titrate to your maintenance dose.
Why Choose G-1 Nutrition for Your Switch?
Our qualified prescribers don't just follow generic conversion charts. We assess your complete Wegovy history to determine the optimal Mounjaro starting dose for your situation.
Common Dose-Related Questions
❓ Can I request a specific starting dose?
You can discuss your preferences with your prescriber, but the final decision should be based on clinical judgement. A good prescriber will explain their reasoning and consider your input, but they shouldn't simply prescribe whatever dose you ask for. If a provider agrees to start you on a high dose without proper assessment, that's a red flag about their clinical standards.
⏰ What if 5mg doesn't feel strong enough?
Give it time. The first four weeks on any new dose are an adjustment period. If after four full weeks you're not experiencing adequate appetite suppression, that's when to discuss increasing to 7.5mg with your prescriber. Don't judge effectiveness based on the first few days.
💊 Is 2.5mg ever enough for weight loss?
Rarely. The 2.5mg dose is designed as a titration dose to help your body adjust, not as a long-term maintenance dose. Most patients need to move to at least 5mg to see meaningful weight loss. However, the four weeks on 2.5mg aren't wasted – they help prepare your system for higher doses.
📈 What's the highest dose I might need?
The maximum dose is 15mg weekly. However, many patients achieve excellent results on 5mg, 7.5mg, or 10mg. Higher isn't automatically better. The goal is to find the lowest effective dose that adequately suppresses your appetite without causing problematic side effects.