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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Best Pre Workout For Weight Loss — UK Prescription Options
When it comes to weight loss in the UK, prescription medication can be a powerful tool alongside diet and exercise. If you're looking for the most effective weight loss support, NHS-licensed options like Mounjaro (tirzepatide) and Wegovy (semaglutide) are available to eligible adults. These GLP-1 and dual-action medications work by helping regulate appetite and supporting you to feel fuller after smaller meals, making your weight management journey more achievable. Understanding what prescription options exist and whether you're eligible is an important first step toward sustainable weight loss.
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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
Three prescription medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist administered as a once-weekly injection. Clinical trials showed average weight loss of 15–21% body weight alongside a reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — A GLP-1 receptor agonist, also injected once weekly. STEP trial data indicated average weight loss of approximately 15% body weight.
- Saxenda (liraglutide) — A GLP-1 agonist administered as a daily injection, with slightly lower average weight loss outcomes than once-weekly options.
All three are prescription-only medicines requiring assessment by a licensed prescriber. Eligibility typically includes adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Use our GLP-1 weight loss calculator to estimate potential weight loss at different doses, and check your starting point with our BMI calculator to understand your eligibility baseline.
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 Prescription in the UK
NHS access to weight loss medication is through specialist tier 3 weight management services, usually requiring a GP referral. Availability varies significantly by region, and waiting lists can be lengthy. Private prescription access is available through GPhC-registered online prescribers following a clinical assessment, without needing an NHS referral — typically costing between £129–£320 monthly depending on dose.
To find out if you're eligible, start a conversation with your GP about your weight loss goals and health history. Alternatively, you can undergo a private clinical assessment with a licensed prescriber. Either route requires honest disclosure of your medical history, current medications, and any contraindications. Remember, prescription medication is most effective when combined with sustainable dietary changes and increased physical activity — not as a replacement for them. Track your progress with our free progress tracker to monitor results over time.
- 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 is the difference between Mounjaro and Wegovy for weight loss?
Both are once-weekly injections, but Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials suggest Mounjaro may produce slightly higher average weight loss (15–21% vs ~15%), but individual results vary significantly. Your prescriber will assess which is more suitable for you.
Can I get weight loss injections on the NHS in the UK?
Yes, Mounjaro and Wegovy are available on the NHS through specialist weight management services (tier 3). You'll need a GP referral and must meet eligibility criteria (BMI 30+ or 27+ with health conditions). NHS availability varies by region and waiting times can be long. Private prescription is an alternative without NHS referral.
Am I eligible for prescription weight loss medication?
UK eligibility typically includes adults with a BMI of 30 kg/m² or above, or 25–29.9 with weight-related conditions (diabetes, hypertension, sleep apnoea). Lower thresholds apply to South Asian, Chinese, Black African, or Black Caribbean adults (BMI 27.5+). Your GP or a licensed prescriber can assess your individual eligibility following a clinical assessment.
How quickly will I lose weight with Mounjaro or Wegovy?
Individual results vary significantly. Clinical trials show average weight loss of 15–21% body weight (depending on medication and dose) over approximately 16–72 weeks, alongside diet and exercise. The NHS recommends sustainable weight loss of 0.5–1 kg per week. Use our weight loss calculator to estimate potential outcomes.
Do I need to follow a diet and exercise plan while taking weight loss medication?
Yes. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. Medication helps regulate appetite and supports feeling fuller, but lasting results depend on sustainable lifestyle changes. Your prescriber will discuss diet and exercise expectations during your assessment.
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.