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 Suppress Appetite Immediately?
Mounjaro (tirzepatide) does not suppress appetite immediately — appetite reduction typically begins within the first week or two, but builds gradually as your dose increases over several weeks. Most people notice significant appetite changes by week 4–8 when they reach a therapeutic dose. In the UK, accessing Mounjaro involves either NHS referral to specialist weight management services or private prescription through an online clinical assessment. Understanding the timeline, costs, and access routes helps you set realistic expectations for your weight management journey.
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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.
Appetite Timeline and UK Private Prescription Costs
Mounjaro works by activating GLP-1 and GIP receptors, which signal fullness to your brain. However, this effect is dose-dependent — it strengthens as your dose increases every 4 weeks during the titration phase. Week 1 at 2.5 mg may cause mild nausea but minimal appetite suppression. By week 5 at 5 mg, many users report noticing reduced hunger. Weeks 9–16 (7.5–10 mg) typically bring more pronounced appetite changes. The maximum dose of 15 mg, reached around week 21, produces the strongest effect.
In the UK, private Mounjaro prescription costs typically range from £150–£320 per month depending on your dose and provider. A 2.5 mg starter pen costs less; a 15 mg maintenance pen costs more. You may need multiple pens during titration. NHS access is available through tier 3 specialist weight management services, though availability and waiting times vary significantly by region. Private online consultations usually cost £30–£60 and are required before prescribing.
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.
NHS vs Private Access and What the Prescription Process Involves
NHS route: Referral from your GP to a specialist weight management service. Assessment typically takes 6–12 weeks or longer depending on waiting lists. Mounjaro may be offered if you meet NICE eligibility criteria (BMI ≥30 or ≥27 with weight-related health conditions like type 2 diabetes or hypertension). Costs are covered by the NHS once prescribed.
Private route: Complete an online consultation with a UK-licensed prescriber within days. After assessment, a prescription is issued and sent to a GPhC-registered pharmacy for dispensing. This route is faster but requires upfront payment. Both routes require a clinical assessment — Mounjaro is prescription-only and cannot be accessed without one. Our GLP-1 weight loss calculator can help you understand projected outcomes at different doses.
- 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.
How quickly does Mounjaro suppress appetite?
Appetite suppression typically begins within 1–2 weeks at the starting dose but is mild. Noticeable appetite reduction usually occurs by week 4–8 as your dose increases. Maximum appetite suppression occurs at maintenance doses (10–15 mg), usually around week 21. Individual responses vary.
How much does Mounjaro cost in the UK privately?
Private prescription costs range from £150–£320 per month depending on dose. Starter doses (2.5–5 mg) cost less; maintenance doses (10–15 mg) cost more. Online consultation fees are typically £30–£60. Always check current pricing with providers, as costs vary.
Can I access Mounjaro through the NHS in the UK?
Yes. You need a GP referral to a specialist tier 3 weight management service. You must meet NICE eligibility criteria (BMI ≥30 or ≥27 with weight-related conditions). Availability and waiting times vary significantly by region and local integrated care boards.
What is the difference between Mounjaro and Wegovy for appetite control?
Mounjaro (tirzepatide) is a dual GIP + GLP-1 agonist; Wegovy (semaglutide) is GLP-1-only. Mounjaro may produce slightly stronger appetite suppression in clinical trials, though individual results vary. Both require prescription and clinical assessment.
Does Mounjaro suppress appetite if I'm not diabetic?
Yes. Mounjaro suppresses appetite through GLP-1 and GIP receptor activation, which works regardless of diabetes status. However, you must still meet UK eligibility criteria (BMI threshold or BMI with weight-related health conditions) to be prescribed it by your GP or 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.