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
Can You Stop and Start Mounjaro in the UK?
Yes, you can stop and restart Mounjaro (tirzepatide), but this must be managed with your prescriber. Stopping suddenly isn't harmful, but restarting after a break requires a new clinical assessment. Weight typically returns gradually once treatment stops. Whether you're on the NHS or accessing Mounjaro privately through a UK prescription, your prescriber will assess whether restarting is appropriate for you based on your current health, eligibility, and treatment goals.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
UK Private Prescription Costs and Access Routes
Private Mounjaro access in the UK is available through GPhC-registered online pharmacies following an online clinical consultation with a UK-licensed prescriber. Costs vary by dose and provider, typically ranging from £129 to £280+ per month depending on the strength you're prescribed. Each KwikPen contains four weekly doses. Stopping and restarting privately means you'll need a new online assessment — prescribers cannot simply resume treatment without reviewing your current health status, weight, and any comorbidities. NHS access is through tier 3 specialist weight management services via GP referral, though regional availability is very limited and waiting lists can be lengthy. If you stop NHS treatment, restarting requires reassessment through the same specialist service. Some people switch between NHS and private routes; this always requires a fresh clinical assessment from the new provider.
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.
Stopping, Restarting, and What Happens to Your Weight
When you stop Mounjaro, appetite gradually returns over 2–4 weeks as the medication leaves your system. Weight typically starts to return, though the rate varies — some people maintain weight loss for months, others regain more quickly. This is not a failure; it reflects how the medication works. If you're considering stopping, discuss this with your prescriber first — they may suggest alternatives like Wegovy (semaglutide) or adjusting your dose instead. Restarting after a break means beginning again at the lowest dose (2.5 mg) and titrating up, which takes 4–5 weeks. Your prescriber will want to understand why you stopped and assess whether the same dose is appropriate now. Track your progress throughout to help inform these conversations with your healthcare team.
- 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.
What happens if I stop Mounjaro suddenly?
Stopping suddenly is not medically harmful — the medication doesn't create physical dependence. However, appetite will gradually return over 2–4 weeks and weight loss effects will fade. Always inform your prescriber before stopping to discuss whether this is the right decision for you or if alternatives exist.
Do I need a new prescription to restart Mounjaro after stopping?
Yes. Whether on the NHS or private prescription, restarting requires a new clinical assessment. Your prescriber needs to confirm you still meet eligibility criteria, review any health changes, and confirm the appropriate starting dose — which will typically be 2.5 mg again.
How much does Mounjaro cost privately in the UK per month?
Private Mounjaro costs vary by provider and dose, typically £129–£280+ per month. Each KwikPen contains four weekly injections. Costs depend on which dose you're prescribed during your titration journey — higher doses cost more. Always confirm the total cost including any consultation fees.
Can I switch between NHS and private Mounjaro treatment?
Yes, you can switch routes, but each switch requires a new clinical assessment from the new provider. Moving from private to NHS means a fresh referral and specialist assessment. Moving from NHS to private requires a new online consultation and prescription. There's no automatic transfer between systems.
Will I regain all my weight if I stop Mounjaro?
Weight regain varies significantly between individuals. Some people maintain loss for months; others regain more quickly. Regain depends on your diet, activity level, and whether you've made sustainable lifestyle changes alongside the medication. Discuss long-term weight management strategies with your prescriber.
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.