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
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Mounjaro 2.5mg: NHS Prescribing and UK Access
Mounjaro 2.5mg is the initial starting dose of tirzepatide, a prescription-only GLP-1 and GIP receptor agonist approved in the UK for weight management. This dose is used for the first four weeks of treatment before escalation. Access in the UK is primarily through NHS tier 3 specialist weight management services, though private prescribing is also available. Understanding how the 2.5mg dose fits into your treatment pathway and NHS eligibility criteria can help you navigate weight management options in the UK.
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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.
NHS Eligibility and Tier 3 Services
Mounjaro 2.5mg is available through NHS specialist tier 3 weight management services for adults who meet specific eligibility criteria. You must have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. NICE (National Institute for Health and Care Excellence) has approved tirzepatide for use within NHS services.
However, NHS access varies significantly by region. Some integrated care boards (ICBs) offer tirzepatide, whilst others prioritise alternative treatments. Waiting lists for tier 3 services can be lengthy in many areas. Your GP can refer you to your local specialist service, but they cannot prescribe Mounjaro directly—only tier 3 specialists can initiate treatment. At your initial 2.5mg dose, your prescriber will assess your response and tolerance before increasing to 5mg after four weeks.
Use our free BMI calculator above to check whether you may fall within NHS eligibility thresholds, and our GLP-1 weight loss calculator to explore projected outcomes at different doses.
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.
Private vs NHS Routes for Mounjaro 2.5mg
If NHS access is unavailable in your area or waiting times are unacceptable, private prescribing through UK-licensed online pharmacies offers an alternative. Private prescribers conduct an online clinical assessment and issue a prescription if Mounjaro is appropriate for you. The 2.5mg starting dose costs typically £129–£160 for a single KwikPen (four weeks' supply) through private providers.
Whether via NHS or private route, the 2.5mg dose serves the same purpose: initial tolerance assessment. After four weeks, if well tolerated, your prescriber will escalate you to 5mg. NHS prescriptions incur standard prescription charges (£9.90 in England), whilst private costs vary by provider. Both pathways require clinical assessment—Mounjaro is never available without a prescription.
- 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.
Can my GP prescribe Mounjaro 2.5mg directly on the NHS?
No. In the UK, Mounjaro (tirzepatide) is only prescribed by NHS tier 3 specialist weight management services, not by GPs. Your GP can refer you to your local tier 3 service, but the specialist team will manage prescribing and dose escalation. This is NICE-approved guidance.
How long do I stay on the 2.5mg starting dose?
The 2.5mg dose is used for the first four weeks (one KwikPen containing four weekly injections). After four weeks, if tolerated well, your prescriber will escalate you to 5mg. Dose increases typically occur every four weeks until you reach your maintenance dose (usually 10–15mg).
What happens if I experience side effects on 2.5mg?
Common side effects at 2.5mg include nausea, diarrhoea, and appetite reduction. Most side effects improve within days or weeks. If side effects are severe, inform your prescriber—they may extend your time on 2.5mg before escalating, or adjust your approach. Do not stop without medical guidance.
Is Mounjaro 2.5mg available on the NHS in my area?
NHS availability varies by region. Some integrated care boards offer tirzepatide, whilst others do not. Ask your GP to check your local tier 3 weight management service. If unavailable via NHS, private prescribing through UK-licensed providers is an option.
How much does Mounjaro 2.5mg cost privately in the UK?
Private Mounjaro 2.5mg typically costs £129–£160 per KwikPen (four-week supply). Prices vary slightly by provider. NHS prescriptions cost the standard £9.90 (England) if accessed through tier 3 services. Track your weight journey using our free progress tracker.
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.