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
Does Mounjaro Wear Off Over Time?
Mounjaro doesn't "wear off" in the traditional sense — your body doesn't build up a tolerance to tirzepatide. However, weight loss results can plateau if you reach a lower weight where a smaller calorie deficit exists. If you stop taking Mounjaro, weight regain is common because the appetite-suppressing effects stop. This guide explains how Mounjaro works over time, what happens when you pause treatment, and the UK cost and access options for getting a Mounjaro prescription — whether through NHS specialist services or private online consultation.
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.
How Mounjaro Works and When Weight Loss Plateaus
Mounjaro (tirzepatide) works by activating two hormone pathways — GIP and GLP-1 — which reduce appetite and help you feel fuller after smaller meals. These effects don't diminish over time in the way tolerance develops with some drugs. However, weight loss can plateau as your body adapts and your metabolism adjusts to your new, lower weight. This is normal biology, not a sign the medication has stopped working. If you reach your target weight and maintain it on Mounjaro, you may stay stable rather than continue losing weight indefinitely.
When you stop taking Mounjaro, the appetite-suppressing effects wear off within days to weeks. Research shows many people regain weight without ongoing treatment or sustained lifestyle changes. This is why healthcare providers discuss long-term management plans — whether continuing Mounjaro long-term or transitioning to lifestyle maintenance. Your Mounjaro KwikPen dose titration (starting at 2.5 mg and increasing up to 15 mg) is designed to find your optimal dose, and remaining on that dose typically maintains results.
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.
UK Access Routes: NHS vs Private Mounjaro Cost
In the UK, you can access Mounjaro through two routes. The NHS route requires referral to a tier 3 specialist weight management service — your GP can refer you. However, NHS availability varies significantly by region and waiting lists can be lengthy. NICE has approved tirzepatide for NHS use, but not all areas have services yet.
The private route is faster. You complete an online consultation with a UK-licensed prescriber, who assesses your eligibility (BMI ≥30, or ≥27 with weight-related conditions like type 2 diabetes or high blood pressure). If approved, you receive a prescription dispensed by a GPhC-registered pharmacy. Private costs typically range from £129–£320 per month depending on your dose. Use our GLP-1 weight loss calculator to estimate potential results before committing to treatment.
- 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.
Does Mounjaro lose effectiveness over time?
No — your body doesn't build up tolerance to tirzepatide. However, weight loss may slow or plateau as you reach a lower weight and your metabolism stabilises. This is normal. Remaining on your current dose typically maintains your weight rather than continuing active loss.
What happens if I stop taking Mounjaro?
The appetite-suppressing effects wear off within days to weeks, and weight regain is common without ongoing treatment or sustained lifestyle changes. Many people regain 50% or more of lost weight within a year of stopping. Long-term management plans should be discussed with your prescriber.
How much does Mounjaro cost on the NHS in the UK?
Mounjaro is free on the NHS if prescribed through a specialist tier 3 weight management service. However, not all UK regions currently offer it, and referral waiting times vary. Contact your GP about local availability.
What's the typical cost of private Mounjaro in the UK?
Private Mounjaro typically costs £129–£320 per month depending on your dose (2.5 mg to 15 mg). Costs vary between private providers. You'll need an online clinical assessment and prescription before dispensing.
Is Mounjaro the same as Wegovy for weight loss?
Both are weight loss injections available in the UK, but they differ. Mounjaro (tirzepatide) is a dual GIP + GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials show Mounjaro may have slightly higher average weight loss (~21% vs ~15%), but individual results vary. Both require prescription and clinical assessment.
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.