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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6 Month Weight Loss with UK Prescription Medication
If you're aiming for meaningful weight loss over six months, prescription medication may be an option worth discussing with your GP. In the UK, several licensed weight management medications are available — either through NHS specialist services or private prescription — that can support a six-month weight loss plan. These work alongside dietary changes and increased physical activity. This guide explains the prescription options available, how they work, eligibility criteria, and how to access them through the NHS or private providers. Individual results vary, but clinical evidence shows these medications may help eligible adults lose between 5–21% of body weight over six months when combined with lifestyle changes.
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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 for Six Months
Three prescription-only medications are licensed in the UK specifically for weight management:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist. Once-weekly injection. Starting dose 2.5 mg, escalating to a maximum of 15 mg. Clinical trials showed participants lost an average of 15–21% of body weight over 72 weeks alongside dietary changes.
- Wegovy (semaglutide) — A GLP-1 receptor agonist. Once-weekly injection. Doses from 0.25 mg to 2.4 mg. STEP trials demonstrated average weight loss of approximately 15% of body weight at 68 weeks.
- Saxenda (liraglutide) — A GLP-1 receptor agonist. Once-daily injection. Doses from 0.6 mg to 3 mg. Evidence supports sustained weight loss for eligible adults.
All three require a prescription following clinical assessment. Individual results vary significantly. A six-month timeframe allows for dose escalation and adaptation, with most results visible by month four to six of treatment.
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 in the UK
NHS access: Mounjaro and Wegovy are available through tier 3 specialist weight management services. You'll typically need a GP referral and may face a waiting list. Availability varies by region (ICB). Your GP can advise whether you meet local criteria.
Private access: Available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. No NHS referral needed. Typically faster access than NHS routes, though you'll pay privately. To find out if you're eligible for either route, book a conversation with your GP — they can assess your BMI, health conditions, and current medications. Use our free BMI calculator above to check your current BMI and see where you fall on NHS eligibility thresholds.
To understand your personal weight loss context, try our GLP-1 weight loss calculator, which can project six-month outcomes at different medication doses. This is for informational purposes only — your prescriber will assess what's suitable for you individually. Remember that prescription weight loss medication works best when combined with a reduced-calorie diet and increased physical activity. Track your progress over the six months using our free progress tracker, logging weekly weight and measurements to stay motivated and accountable to your goals.
- 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.
Can I get Mounjaro or Wegovy on the NHS for six-month weight loss?
Yes, if you meet NHS eligibility criteria. You must have a BMI of 30 or above (or 27+ with weight-related health conditions like type 2 diabetes, hypertension, or sleep apnoea). Access is through tier 3 specialist weight management services via GP referral. Availability varies by region. Waiting times can be several months in many areas.
How much weight can I expect to lose in six months?
Clinical evidence suggests eligible adults may lose between 5–21% of body weight over six months, depending on the medication, dose, and adherence to lifestyle changes. Individual results vary significantly. Mounjaro users averaged 15–21% loss in trials; Wegovy users averaged around 15%. This is not assured for everyone.
What's the difference between Mounjaro and Wegovy for six-month weight loss?
Both are once-weekly injections licensed in the UK. Mounjaro is a dual GIP/GLP-1 agonist; Wegovy is a GLP-1 agonist only. Mounjaro may work slightly faster for some people due to dual action. Both require clinical assessment. Your prescriber will advise which is most suitable for you.
Do I need to diet and exercise while taking weight loss medication?
Yes. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. They're not a replacement for lifestyle changes — they're a support. Clinical trials showed weight loss only when medication was combined with behaviour change.
What's the NHS eligibility criteria for six-month weight loss medication?
You must have a BMI of 30 kg/m² or above, OR a BMI of 27–29.9 kg/m² with at least one weight-related health condition (type 2 diabetes, prediabetes, high blood pressure, abnormal cholesterol, sleep apnoea, or cardiovascular disease). Use our free BMI calculator to check your BMI and discuss eligibility with your GP.
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.