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 Do You Stay On Mounjaro?
There is no set end date for Mounjaro treatment — how long you take it depends on your individual health goals, weight loss progress, and how well you tolerate the medication. Most people who benefit from tirzepatide continue taking it long-term, typically for at least one year or longer, though some may stop after reaching their target weight or if side effects become difficult to manage. Your GP or prescriber will review your progress regularly and discuss whether continuing Mounjaro remains right for you.
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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.
Mounjaro Treatment Duration and Dose Titration
Mounjaro is not a short-term course — it's a long-term weight management tool. Unlike antibiotics, which you take for a fixed period, Mounjaro treatment continues as long as it's helping you and you're tolerating it well.
The first phase is dose titration, where you start at 2.5 mg and increase by 2.5 mg every 4 weeks until you reach an effective dose (typically 5–15 mg). This titration phase usually lasts 16–20 weeks. Once you're on a stable maintenance dose, you continue taking it weekly as long as your prescriber agrees it's beneficial.
Clinical data shows that people who stop Mounjaro often regain weight relatively quickly — usually within weeks to months. This is why most NHS and private guidance recommends staying on tirzepatide long-term rather than using it as a temporary fix. If you're not losing weight after 3 months on your maintenance dose, your prescriber may consider stopping it or switching to an alternative, such as Wegovy (semaglutide).
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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 Do People Stop Taking Mounjaro?
You may stop Mounjaro if:
- You reach your target weight — though most people continue long-term to maintain results
- Side effects become unmanageable — nausea, diarrhoea, or constipation that doesn't improve over time
- It stops being effective — no weight loss after 3 months on a stable dose
- Your health circumstances change — pregnancy, new diagnosis, or medication conflict
- You choose to stop — your choice is always respected, though you should discuss this with your prescriber first
If you decide to stop, you simply stop taking the weekly injection. There is no withdrawal period or tapering required. However, weight regain is common, so discuss strategies with your GP before stopping.
- 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 stay on Mounjaro indefinitely?
Yes — many people take Mounjaro long-term (1 year or more) with ongoing prescriber monitoring. There's no maximum duration recommended in UK guidance. However, this is reviewed annually, and if you're no longer losing weight or experiencing unmanageable side effects, your GP may suggest stopping or switching medications.
How long does it take to reach the right Mounjaro dose?
The dose titration phase typically takes 16–20 weeks. You start at 2.5 mg and increase by 2.5 mg every 4 weeks. Most people find their effective dose between 5 mg and 15 mg. Your prescriber may adjust this based on your weight loss progress and side effect tolerance.
What happens to your weight when you stop Mounjaro?
Weight regain is common after stopping tirzepatide. Studies show people typically regain weight within weeks to months if lifestyle changes aren't maintained. This is why NHS and private providers recommend long-term treatment rather than short-term use. Your progress tracker can help monitor this.
How often does your prescriber review you on Mounjaro?
On the NHS, reviews typically happen every 3–6 months. Private prescribers usually check in monthly initially, then every 3 months once stable. Your prescriber will assess weight loss, side effects, blood pressure, and whether treatment should continue or if an alternative like Wegovy might suit you better.
Do you need blood tests while taking Mounjaro?
Yes — baseline blood tests (kidney function, liver function, pancreatic markers) are recommended before starting tirzepatide. Annual monitoring is advised, particularly if you have diabetes or kidney concerns. Your GP will arrange these as part of ongoing care.
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.