The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
How Long Can You Take Mounjaro?
Mounjaro (tirzepatide) is a prescription-only once-weekly injection licensed for weight management in UK adults. Many people ask how long they can take it — the answer depends on your individual response, weight loss goals, and ongoing health needs. Unlike short-term diet plans, Mounjaro is typically used as a longer-term treatment, potentially for years, as long as it remains effective and well-tolerated. Your GP or prescriber will monitor your progress and adjust your treatment plan based on how you respond. This guide covers the duration of Mounjaro treatment in the UK context.
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Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Duration and Maintenance of Mounjaro Treatment
There is no fixed time limit for how long you can take Mounjaro. Many people remain on Mounjaro for 12 months, 2 years, or longer — provided the medication continues to help them lose or maintain weight and they tolerate it well. Clinical trials have demonstrated safety over periods of up to 72 weeks, but prescribers increasingly manage patients on longer-term treatment in real-world practice.
Once you reach your target weight or a plateau, your prescriber may recommend continuing Mounjaro as a maintenance dose to prevent weight regain. Weight cycling (losing weight then regaining it) is common when stopping weight loss medications, so many UK specialist services now recommend ongoing treatment for suitable candidates.
- Dose titration phase: typically 16–20 weeks to reach your optimal dose (2.5 mg up to 15 mg)
- Active weight loss phase: varies by individual, typically 12–18 months
- Maintenance phase: ongoing, as needed, to sustain results
Your UK prescription can be renewed indefinitely as long as your prescriber confirms you meet eligibility criteria and the treatment remains beneficial for your health.
Clinically BackedWeight Loss
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
When to Stop Mounjaro and Managing Discontinuation
You may decide to stop Mounjaro if you no longer wish to continue, or your prescriber may recommend stopping if you develop side effects you cannot tolerate, or if new medical conditions make it unsuitable. Stopping suddenly is safe — tirzepatide does not cause physical dependency — but be aware that weight regain is common within weeks to months of stopping.
If you stop Mounjaro, weight typically returns because appetite regulation returns to baseline. To prevent rapid regain, many people transition to sustainable diet and exercise habits during treatment, rather than relying on Mounjaro alone. Our free GLP-1 weight loss calculator can help you project realistic timelines and outcomes. Discuss any plans to stop with your prescriber — they may suggest tapering your dose or transitioning to lifestyle support.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Can you take Mounjaro indefinitely?
Yes, Mounjaro can be taken indefinitely as long as it remains effective, you tolerate it well, and you continue to meet NHS or private prescription eligibility criteria. Many UK patients use it as ongoing maintenance therapy after reaching their weight loss goal. Your prescriber reviews this regularly.
What happens if you stop taking Mounjaro?
Stopping Mounjaro is safe and does not cause withdrawal symptoms. However, appetite returns to normal and weight regain is common — typically within weeks to months. To minimise regain, focus on sustainable lifestyle habits alongside or after treatment.
How long does it take to see results with Mounjaro?
Weight loss typically begins within 4–8 weeks, with noticeable results by 12 weeks. However, you need to reach your optimal dose first (dose titration takes 16–20 weeks), so full results may take 4–6 months or longer. Individual timelines vary.
Is there a maximum time limit for Mounjaro on the NHS?
There is no formal NHS maximum duration. Access varies by region (ICB), and specialist services manage patients long-term if the medication remains beneficial. However, NHS availability and waiting lists vary significantly across the UK.
Can you take Mounjaro and Wegovy at the same time?
No — Mounjaro and Wegovy should never be taken together as they work through similar pathways. Only one GLP-1 or GIP/GLP-1 medication should be used at a time. Any switch between medications must be managed by your prescriber with a gap between injections.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.