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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2.5mg Mounjaro Weight Loss: NHS Eligibility & Starting Dose
The 2.5mg dose is where Mounjaro treatment begins in the UK. This starting dose is used for 4 weeks to allow your body to adjust before escalating. While 2.5mg is not a maintenance dose, it's an important part of the dose titration process. Understanding what to expect at this stage — alongside NHS eligibility criteria and how the UK prescribing pathway works — helps you prepare for your weight loss journey. MyWeightCheck explains the NHS context, NICE guidance, and realistic expectations for starting Mounjaro 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 & NICE Guidance for Mounjaro in the UK
Mounjaro (tirzepatide) was approved by NICE in 2024 for use within NHS specialist weight management services, making it available through the NHS in England, Scotland, Wales, and Northern Ireland — though regional availability varies.
NHS eligibility criteria:
- BMI of 30 kg/m² or above, OR
- BMI of 27–29.9 kg/m² with at least one weight-related health condition (type 2 diabetes, prediabetes, hypertension, dyslipidaemia, obstructive sleep apnoea, or history of cardiovascular disease)
- For South Asian, Chinese, Black African, or Black Caribbean adults: lower thresholds apply (BMI 27.5 or above)
Access is through tier 3 specialist weight management services, not standard GP prescription. Your GP can refer you, but waiting times vary significantly by region. The SURMOUNT-1 trial showed that tirzepatide helped participants lose an average of 15–21% body weight alongside reduced-calorie diet and increased physical activity — though individual results vary considerably.
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.
Starting Mounjaro: Dose 2.5mg & NHS vs Private Access
The 2.5mg starting dose is given as a once-weekly weekly weight loss injection using the Mounjaro KwikPen. You remain on this dose for weeks 1–4, then escalate to 5mg in week 5 (minimum 4 weeks between increases). At 2.5mg, side effects are typically milder than at higher doses, though nausea and gastrointestinal symptoms are common.
NHS vs private route: NHS access requires referral to tier 3 services with potential waiting lists of months. Private access is available through GPhC-registered online pharmacies following an online clinical assessment — faster but at cost (approximately £129–£320 per month depending on dose). Both routes provide the same medication and require a UK-licensed prescriber's assessment. Use our GLP-1 weight loss calculator to estimate potential outcomes at different doses, and try our BMI calculator to check your current eligibility criteria.
- 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 much weight will I lose on 2.5mg Mounjaro?
2.5mg is a starting dose, not a maintenance dose, so weight loss at this stage is typically modest. Full weight loss potential is realised at higher maintenance doses (10–15mg). Clinical trials showed average losses of 15–21% body weight at maximum dose alongside lifestyle changes. Individual results vary based on adherence, diet, exercise, and personal metabolism. Your prescriber can discuss realistic expectations for your situation.
What are the side effects of 2.5mg Mounjaro?
Very common side effects at 2.5mg include nausea, diarrhoea, constipation, vomiting, and stomach pain. These typically improve as your body adjusts over 4 weeks. Common side effects include indigestion, fatigue, dizziness, and injection site reactions. Serious side effects are rare but include severe stomach pain (possible pancreatitis), gallbladder problems, and serious allergic reactions. Always report concerns to your prescriber immediately.
Am I eligible for Mounjaro on the NHS in the UK?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with a weight-related health condition (diabetes, hypertension, sleep apnoea, cardiovascular disease). Lower thresholds apply for South Asian, Chinese, Black African, or Black Caribbean adults. Access is through NHS specialist tier 3 weight management services, not standard GP prescription. Ask your GP for a referral to check availability in your region.
How long do I stay on 2.5mg Mounjaro?
The 2.5mg dose is used for exactly 4 weeks (weeks 1–4) as part of the dose titration schedule. After 4 weeks, you escalate to 5mg and continue the same escalation pattern every 4 weeks until you reach your maintenance dose or the dose your prescriber recommends. Staying on each dose for the full 4 weeks allows your body to adjust and helps your prescriber monitor how you're tolerating the medication.
How do I get Mounjaro on the NHS vs privately in the UK?
NHS route: Ask your GP for a referral to a tier 3 specialist weight management service. NICE has approved Mounjaro for NHS use, but regional availability and waiting lists vary (potentially several months). Private route: Consult with a UK-licensed prescriber through a GPhC-registered online pharmacy. Private access is typically faster (days to weeks) but involves a consultation fee and medication cost (£129–£320+ per month). Both routes require clinical assessment before prescription.
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.