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 2.5 Mg — NHS Starting Dose in the UK
Mounjaro 2.5 mg is the starting dose of tirzepatide prescribed through NHS specialist weight management services in the UK. This initial injection helps your body adapt to the medication before doses are gradually increased. Understanding how the NHS prescribes Mounjaro, who is eligible, and how the dose progression works can help you understand the treatment pathway. Check your BMI using our free BMI calculator to see if you may be eligible for weight management support on the NHS.
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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 Mounjaro 2.5 Mg Starting Dose
Mounjaro 2.5 mg is the first dose when tirzepatide is prescribed through NHS tier 3 specialist weight management services. You receive this starting injection for the first 4 weeks, allowing your body to tolerate the medication before escalation.
NHS eligibility for Mounjaro includes:
- BMI of 30 kg/m² or above (obesity), OR
- BMI of 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, hypertension, sleep apnoea, or cardiovascular disease
- For South Asian, Chinese, Black African, or Black Caribbean adults: lower thresholds may apply (BMI 27.5+)
- Adults aged 18 and over
Access is through NICE-approved tier 3 services, typically accessed via GP referral. NICE guidance approves tirzepatide for specialist weight management, though availability varies significantly by region and local commissioning decisions. The 2.5 mg starting dose allows your prescriber to assess tolerance before progression.
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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 Route for Mounjaro 2.5 Mg
NHS route: Mounjaro 2.5 mg is available through specialist NHS tier 3 weight management services following GP referral. Access is free but involves waiting lists that can extend several months to over a year in many areas. Regional variation is significant—some ICBs have more capacity than others.
Private route: Tirzepatide is available privately through GPhC-registered online prescribing services. Private prescriptions typically progress doses more flexibly. Costs range from approximately £129–£200+ monthly depending on dose and provider. You can use our free GLP-1 weight loss calculator to project potential outcomes at different doses, whether pursuing NHS or private routes.
- 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 is Mounjaro 2.5 mg dosed on the NHS?
The 2.5 mg dose is administered as a once-weekly injection for weeks 1–4. After 4 weeks, if tolerated, your NHS prescriber will increase to 5 mg weekly. Each KwikPen contains 4 doses, providing a 4-week supply. You inject subcutaneously (under the skin) in the stomach, thigh, or upper arm.
What happens after the 2.5 mg starting dose?
Your prescriber assesses tolerance at week 4. If well tolerated, the dose increases to 5 mg for weeks 5–8. Subsequent escalations occur every 4 weeks up to a maximum of 15 mg weekly. The pace depends on your individual response and any side effects experienced.
How long do I stay on 2.5 mg Mounjaro?
Typically 4 weeks. This starting period allows your body to adjust to tirzepatide's dual GIP and GLP-1 action. If you experience significant side effects during week 1–4, your NHS prescriber may extend this phase before escalating. Always follow your prescriber's specific guidance.
Can I access Mounjaro 2.5 mg through my GP directly?
No. Mounjaro is initiated through NHS tier 3 specialist weight management services, not standard GP prescribing. You need a GP referral to the specialist service. Waiting times vary by region from several months upwards, depending on local capacity and demand.
How does 2.5 mg Mounjaro compare to 5 mg?
2.5 mg is a dose escalation step, not a therapeutic dose. Clinical trial data shows meaningful weight loss occurs at higher doses (5 mg and above). The 2.5 mg phase is primarily for tolerance assessment, not for achieving weight loss targets.
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.