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 Start Mounjaro at 5 mg?
No — Mounjaro (tirzepatide) does not start at 5 mg in the UK. The standard starting dose is 2.5 mg once weekly for the first four weeks. This lower initial dose helps your body adjust to the medication and allows your prescriber to monitor how you respond before increasing to higher doses. Understanding the tirzepatide dosing schedule is essential if you're considering this prescription-only weight management injection. Use our free BMI calculator to check your current health status, and our GLP-1 weight loss calculator can help you understand potential outcomes at different doses.
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.
The Mounjaro UK Dosing Schedule and Titration Timeline
Mounjaro follows a strict dose titration schedule in the UK, where each dose is increased every four weeks if tolerated:
- Weeks 1–4: 2.5 mg (starting dose)
- Weeks 5–8: 5 mg (first escalation)
- Weeks 9–12: 7.5 mg
- Weeks 13–16: 10 mg
- Weeks 17–20: 12.5 mg
- Week 21+: 15 mg (maximum dose)
Your prescriber may keep you on 5 mg if this is your optimal maintenance dose — you don't have to reach the maximum. The slow titration approach reduces nausea and other side effects. Each KwikPen contains four weekly doses, so one pen covers one dose level.
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 Private and NHS Access to Mounjaro
Private route: Online consultations with UK-licensed prescribers assess your eligibility, and if approved, you'll receive a prescription dispensed through a GPhC-registered pharmacy. Most private providers follow the standard 2.5 mg start, though some may offer flexibility based on clinical assessment. Costs typically range from £129–£320 per month depending on dose and provider.
NHS route: NICE approval means Mounjaro is available through NHS tier 3 specialist weight management services, but access varies significantly by region and waiting lists can be lengthy. Your GP can refer you, but you'll be assessed at specialist tier 3 clinics where standard dosing protocols apply.
- 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.
Why does Mounjaro start at 2.5 mg instead of 5 mg?
The 2.5 mg starting dose allows your body to adapt to the medication and helps your prescriber monitor tolerance before increasing. This gradual titration reduces gastrointestinal side effects like nausea and vomiting. Clinical guidelines recommend this approach for safety and tolerability.
How long does it take to reach the 5 mg dose?
It takes four weeks at the 2.5 mg starting dose, then you move to 5 mg in weeks 5–8. If you're prescribed privately, your prescriber may adjust this timeline based on your individual response and side effects.
Can you stay on 5 mg Mounjaro long-term?
Yes, many people achieve their weight loss goals and maintain them on 5 mg. You don't need to escalate to higher doses if 5 mg is working effectively for you and your prescriber agrees it's your optimal maintenance dose.
What's the difference between Mounjaro and Wegovy dosing in the UK?
Mounjaro starts at 2.5 mg weekly and reaches a maximum of 15 mg. Wegovy (semaglutide) starts at 0.25 mg weekly and reaches 2.4 mg maximum. Mounjaro's dual GIP and GLP-1 mechanism means different dosing schedules and potentially different weight loss outcomes between the two medications.
Is the Mounjaro dosing schedule different on the NHS versus private prescription?
The standard titration schedule is the same on both NHS and private routes — starting at 2.5 mg with four-week intervals. However, private prescribers may have slightly more flexibility in adjusting the timeline based on your individual circumstances and side effects.
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.