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 Mounjaro Help You Lose Weight in the UK?
Yes, Mounjaro can help with weight loss for eligible UK adults. This prescription-only injection contains tirzepatide, a dual GIP and GLP-1 receptor agonist that may reduce appetite and support feeling fuller after smaller meals. Clinical trials showed participants lost an average of 15–21% of their body weight alongside a reduced-calorie diet and increased physical activity. However, individual results vary significantly, and access through the NHS depends on specific eligibility criteria and referral to specialist services. Understanding how Mounjaro works, who can access it, and the differences between NHS and private routes will help you make an informed decision.
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 Specialist Services
In the UK, Mounjaro is available through both NHS specialist weight management services and private prescribing. NHS eligibility criteria require a BMI of 30 kg/m² or above, or 25–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or obstructive sleep apnoea. NICE (the National Institute for Health and Care Excellence) has approved tirzepatide for use within NHS tier 3 and tier 4 specialist weight management services.
Access is not through your GP directly — you must be referred to a specialist weight management service by your GP. These services provide multidisciplinary support including dietary advice, physical activity guidance, and psychological support alongside medication. Waiting times vary significantly by region, with some areas reporting waiting lists of several months to over a year. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply due to higher health risks at lower weights.
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.
NHS vs Private Access — What's the Difference?
The NHS route offers the medication at no upfront cost once prescribed, but requires a GP referral and assessment by a specialist team. The NHS may also cover the cost of the Mounjaro KwikPen and clinical monitoring. However, NHS availability is limited and regional — not all areas have specialist services with capacity to prescribe tirzepatide.
The private route involves an online consultation with a UK-licensed prescriber, who will assess your eligibility. If approved, your prescription is dispensed by a GPhC-registered pharmacy. Private Mounjaro costs vary by dose and provider (typically £130–£280 per month). Private prescribing offers faster access without waiting lists, but you pay upfront. Both routes require an initial assessment — Mounjaro cannot be obtained without a prescription from a qualified healthcare professional.
- 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 can I expect to lose with Mounjaro on the NHS?
In clinical trials (SURMOUNT-1), participants lost an average of 15–21% of body weight over 72 weeks at the highest dose. However, individual results vary significantly. Weight loss depends on your starting weight, adherence to a reduced-calorie diet, physical activity, and other personal factors. Your specialist team will discuss realistic expectations for you during assessment.
Will my GP prescribe Mounjaro directly?
No. Mounjaro on the NHS is only prescribed by specialist tier 3 or tier 4 weight management services. Your GP must refer you to your local specialist service for assessment. Private Mounjaro can be prescribed by a UK-licensed prescriber via online consultation without a GP referral, though your GP should still be informed.
How does Mounjaro (tirzepatide) differ from Wegovy (semaglutide)?
Both are once-weekly injections, but Mounjaro is a dual GIP and GLP-1 receptor agonist, whilst Wegovy is a GLP-1 agonist only. Mounjaro may have a slightly stronger effect in clinical trials, though individual responses vary. Eligibility criteria are similar. Your prescriber will advise which is more suitable based on your health profile and availability in your region.
What happens if I'm not eligible for NHS Mounjaro?
If you don't meet NHS criteria or are on a waiting list, you can explore private prescribing. Online consultations assess your individual health to determine suitability. Private Mounjaro requires a valid prescription and is dispensed by registered UK pharmacies. Costs vary, and you'll need to cover the full cost yourself. Some people use the private route whilst waiting for NHS assessment.
Can I use the BMI calculator to check my eligibility?
Yes — our free BMI calculator above will instantly show your BMI and the NHS category it falls into. If your BMI is 30 or above, or 25–29.9 with a weight-related health condition, you may be eligible to ask your GP for a referral to a specialist service. However, a prescriber or specialist team must conduct a full clinical assessment before Mounjaro can be prescribed.
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.