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
What is the Mounjaro Starting Dose in the UK?
The Mounjaro starting dose in the UK is 2.5mg, administered as a once-weekly injection via a pre-filled KwikPen device. This initial dose helps your body adjust to tirzepatide, the active ingredient in Mounjaro. After 4 weeks at the starting dose, your prescriber may gradually increase your dose depending on your tolerance and response. Understanding the UK prescribing pathway, NHS eligibility, and what to expect from dose titration is essential if you're considering this weight management treatment. Use our GLP-1 weight loss calculator to explore potential outcomes, and our BMI calculator to check where you stand against NHS thresholds.
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.
NHS Eligibility and the UK Prescribing Pathway for Mounjaro
In the UK, Mounjaro is licensed for weight management in adults with a BMI of 30 kg/m² or above, or 25–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. NICE has approved tirzepatide (Mounjaro) for use within NHS specialist tier 3 weight management services, though regional availability varies significantly.
Access through the NHS typically requires referral from your GP to a specialist multidisciplinary weight management service. Once assessed, your prescriber will determine if the 2.5mg starting dose is appropriate for you. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds (27.5 kg/m² and above) may apply because these groups face higher health risks at lower body weights.
- NHS route: GP referral to tier 3 specialist service; waiting lists vary by region
- Private route: Online clinical assessment with a UK-licensed prescriber; prescription dispensed by a GPhC-registered pharmacy
- Starting dose: 2.5mg once weekly for weeks 1–4
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.
Mounjaro Dose Titration: What Happens After the Starting Dose
After your initial 4 weeks on the 2.5mg starting dose, your prescriber will assess your tolerance and response. If you've tolerated the dose well, it typically increases to 5mg for weeks 5–8. Dose escalation continues at 4-week intervals—7.5mg, 10mg, 12.5mg, and finally 15mg—allowing your body to adapt gradually and minimising side effects like nausea or gastrointestinal discomfort.
The maximum maintenance dose is 15mg once weekly. However, not everyone reaches the highest dose; your prescriber will work with you to find the dose that balances effectiveness with tolerability. When comparing Mounjaro vs Wegovy, tirzepatide's dual GIP and GLP-1 mechanism may deliver slightly greater average weight loss, though individual results vary significantly. Track your progress with our free progress tracker as you adjust to each new dose.
- 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 is the Mounjaro starting dose in the UK?
The Mounjaro starting dose is 2.5mg, injected once weekly for 4 weeks. This allows your body to adjust to tirzepatide before your prescriber considers increasing the dose. The maximum dose is 15mg once weekly.
How do I access Mounjaro on the NHS?
You'll need a GP referral to a specialist tier 3 weight management service. NICE has approved tirzepatide for NHS use, but availability depends on your region and local ICB funding. Waiting lists can be lengthy in many areas.
Can I get Mounjaro faster through a private prescription?
Yes. Private prescribers can assess you online and issue a prescription without NHS referral. A GPhC-registered pharmacy then dispenses the medication. Costs vary, typically £129–£320 per month depending on dose.
Who is eligible for Mounjaro in the UK?
Adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions (diabetes, high blood pressure, cardiovascular disease) may be eligible. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at a BMI of 27.5 or above.
What happens if I can't tolerate the 2.5mg starting dose?
Side effects like nausea are common initially but usually improve within a few days to weeks. Your prescriber may delay dose escalation or recommend slower titration. Never stop or change your dose without medical guidance.
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.