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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5 Month Weight Loss with UK Prescription Medication
Losing weight over a 5-month period is an achievable goal for many UK adults, especially with support from prescription medication. If you have a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure, you may be eligible for prescription weight management treatment. The UK offers several licensed options including Mounjaro and Wegovy, both available through NHS specialist services or private prescription. This guide explains how these medications work, what you might expect in 5 months, and how to explore whether they're suitable for you.
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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 Prescription Weight Loss Options
Three main prescription medications are licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, taken once weekly by injection. In clinical trials, participants lost an average of 15–21% of their body weight over 72 weeks alongside a reduced-calorie diet and exercise.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, also once weekly. Clinical trials showed average weight loss of around 15% body weight over 68 weeks.
- Saxenda (liraglutide) — a GLP-1 receptor agonist administered as a daily injection, with similar weight loss outcomes to Wegovy.
All three are prescription-only and require a clinical assessment by a UK-licensed prescriber to confirm eligibility. Individual results vary significantly based on adherence, diet, physical activity, and individual metabolism. Over a 5-month period, realistic weight loss typically ranges from 3–8 kg (approximately 7–18 lbs or 0.5–1 stone), though some people experience more substantial results.
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 — Finding Your Route
In the UK, you can access prescription weight loss medication through two main routes: NHS specialist weight management services or private online prescribing. NHS access requires a referral from your GP to a tier 3 or tier 4 weight management service in your area. Availability varies significantly by region, and waiting lists can be lengthy — sometimes months to years depending on your local Integrated Care Board (ICB). Private access is faster; you complete an online clinical assessment with a UK-licensed prescriber and, if eligible, receive a prescription dispensed by a GPhC-registered pharmacy. Whichever route you choose, your prescriber will assess your BMI, health history, and any weight-related conditions to confirm you meet eligibility criteria. Start the conversation with your GP, who can advise on NHS options in your area or discuss what private options might look like for you.
- 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 lose a significant amount of weight in 5 months with prescription medication?
Yes, 5 months is a reasonable timeframe. Most people taking Mounjaro or Wegovy lose between 3–8 kg over this period when combined with a reduced-calorie diet and physical activity. Some lose more. Individual results vary based on starting weight, metabolism, medication dose, and lifestyle adherence. Use our GLP-1 weight loss calculator to estimate potential loss at different doses.
Who is eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 or above, or 27 or above if you have a weight-related health condition such as type 2 diabetes, prediabetes, high blood pressure, or cardiovascular disease. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may be eligible at lower BMI thresholds due to higher health risks at lower weights. Check your BMI using our free BMI calculator, then speak to your GP.
How long does it take to reach the maximum dose of Mounjaro or Wegovy?
Dosing is gradual to allow your body to adjust and minimise side effects. Mounjaro typically escalates over 16–20 weeks to reach 15 mg. Wegovy escalates over approximately 16 weeks to reach 2.4 mg. This means you may still be escalating doses within a 5-month window, which can affect total weight loss in that period.
What's the difference between NHS and private access for weight loss medication?
NHS access is free but requires a GP referral and specialist assessment; waiting times vary by region. Private online prescribing is faster and doesn't require NHS referral but involves a cost (typically £129–£320 per month depending on dose). Both routes require a clinical assessment to confirm eligibility.
What should I do first if I want to explore prescription weight loss in 5 months?
Book an appointment with your GP. Discuss your weight loss goals and ask about NHS tier 3 weight management services in your area. Your GP can also advise whether private prescribing might be suitable. Bring your current height and weight so your GP can calculate your BMI, or check your BMI in advance using our free BMI calculator on this page.
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.