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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Habitual Weight Loss — UK Prescription Medication Options
If you're looking for support with habitual weight loss, prescription medications are now available in the UK for eligible adults. Three main options—Mounjaro, Wegovy, and Saxenda—are licensed for weight management and can be prescribed through NHS specialist services or private online prescribing following a clinical assessment. This guide explains how these medications work, who can access them, and the practical steps to explore whether prescription support is right for your situation.
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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.
UK-Licensed Weight Loss Medications Explained
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist injection taken once weekly. In clinical trials, it helped participants lose an average of 15–21% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) is a GLP-1 receptor agonist injected once weekly. Clinical trial data showed average weight loss of approximately 15% body weight at the highest dose, with individual results varying significantly.
Saxenda (liraglutide) is a daily GLP-1 injection administered by pen. It has been available longer than Mounjaro and Wegovy and offers an alternative for those preferring daily dosing.
All three are prescription-only medicines. Your eligibility depends on your BMI, weight-related health conditions, and overall health profile. Try our BMI calculator above to check where you currently sit, and use our GLP-1 weight loss calculator to explore potential outcomes at different doses if you're considering this route.
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 Access vs Private Prescribing — Your Pathways
NHS route: Weight loss medications are available through NHS specialist tier 3 weight management services, typically accessed via GP referral. However, availability varies significantly by region, and waiting lists can be lengthy in many areas.
Private route: You can obtain a prescription from a UK-licensed prescriber through a private online consultation without an NHS referral. A GPhC-registered pharmacy will then dispense the medication. This offers faster access but involves out-of-pocket costs, typically £129–£320 per month depending on dose.
Speak to your GP first. They can assess your individual situation, explain eligibility criteria, and discuss whether prescription weight loss medication is appropriate for your habitual weight management goals. Your GP can also advise on combined approaches—medications work best alongside dietary changes and physical activity.
- 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 does "habitual weight loss" mean?
Habitual weight loss refers to sustained, ongoing weight management over months or years—not rapid short-term loss. It typically involves consistent lifestyle changes, dietary improvements, and sometimes medication support. This gradual approach is more sustainable and less likely to result in rapid regain.
Am I eligible for prescription weight loss medication on the NHS?
Broadly, yes, if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. Eligibility varies by region and requires assessment through your GP or a specialist service. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds.
How quickly will I lose weight on prescription medication?
Individual results vary significantly. Clinical trials showed average losses of 15–21% body weight over several months, but some people lose more, others less. Medications work best alongside a reduced-calorie diet and increased physical activity. Expect gradual loss rather than dramatic change—typically 0.5–1 kg per week.
What's the difference between Mounjaro and Wegovy?
Mounjaro uses a dual GIP and GLP-1 mechanism; Wegovy uses GLP-1 only. Both are once-weekly injections. Clinical trials suggest Mounjaro may support slightly higher average weight loss, but individual responses vary. Both require prescription and clinical assessment. Your prescriber will advise which suits you best.
Can I get these medications if I don't have a health condition, just obesity?
Yes. UK eligibility includes adults with a BMI of 30 or above, regardless of other health conditions. You don't need type 2 diabetes or high blood pressure to qualify. However, a prescriber must still assess your suitability, medical history, and whether medication is appropriate for your situation.
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.