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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Weight Loss in 3 Months — UK Prescription Options
Losing weight in 3 months is possible with the right approach, and prescription medications may help eligible adults achieve meaningful results alongside lifestyle changes. In the UK, three licensed weight loss medications are available through NHS specialist services and private prescribing: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These work by reducing appetite and helping you feel fuller after smaller meals. Clinical trials show these medications support weight management alongside a reduced-calorie diet and increased physical activity. Whether you're eligible depends on your BMI, health conditions, and individual circumstances — your GP can help you explore your options for effective weight loss in the UK.
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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 3-Month Goals
Three prescription-only weight loss medications are currently licensed in the UK for weight management. Mounjaro (tirzepatide) is a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist, helping regulate appetite and blood sugar. In clinical trials, Mounjaro helped participants lose an average of 15–21% of their body weight — though individual results vary significantly. Wegovy (semaglutide) is also a once-weekly injection that activates the GLP-1 pathway; clinical trials showed average weight loss of around 15% of body weight over 68 weeks.
Saxenda (liraglutide) is a daily injection (not weekly) with slightly different dosing. All three require a prescription following a clinical assessment, and eligibility depends on your BMI and health profile. For weight loss in 3 months specifically, you would typically be starting on a low dose and titrating upwards, so maximum effectiveness may not be reached within that timeframe. Realistic weight loss on these medications, combined with a reduced-calorie diet and exercise, is typically 0.5–1 kg per week, meaning 6–12 kg over 3 months — though individual results vary based on dose, adherence, and personal factors.
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 — How to Get Started
NHS access: You can discuss weight loss medication options with your GP, who may refer you to a specialist tier 3 weight management service if eligible. NHS eligibility requires a BMI of 30 or above, or 27–29.9 with a weight-related health condition (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). However, NHS waiting lists for specialist services are lengthy in many regions — waiting times can exceed 12 months in some areas.
Private access: UK-licensed prescribers offer online consultations and prescription weight loss medication through GPhC-registered pharmacies. This pathway is faster but involves out-of-pocket costs (typically £129–£320 per month depending on dose). Whichever route you choose, use our free GLP-1 weight loss calculator to estimate potential outcomes, and our BMI calculator to check your starting point — then book a GP appointment to discuss whether prescription medication is right 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.
How much weight can I realistically lose in 3 months on Mounjaro or Wegovy?
On average, people lose 0.5–1 kg per week with prescription weight loss medication combined with a reduced-calorie diet and exercise, equating to approximately 6–12 kg over 3 months. However, you start on a low dose and increase gradually, so maximum effectiveness may not be reached in 3 months. Individual results vary based on dose, diet adherence, exercise, and metabolism. Clinical trials showed average losses of 15–21% body weight over longer periods (68+ weeks).
What is the eligibility criteria for UK prescription weight loss medication?
You're eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with a weight-related health condition (type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, sleep apnoea, or cardiovascular disease). For people of South Asian, Chinese, Black African, or Black Caribbean heritage, eligibility thresholds may be lower. Your GP or a licensed prescriber will assess your individual circumstances.
Can I access weight loss injections through the NHS for a 3-month programme?
Yes, you can be referred to an NHS specialist weight management service via your GP if eligible. However, NHS waiting lists are often 6–12 months or longer depending on your region. Private online prescribing offers faster access but requires payment. Either way, any programme requires medical oversight and is most effective when combined with diet and lifestyle changes.
Are Mounjaro and Wegovy suitable for weight loss specifically in 3 months?
Both medications can support weight loss within 3 months, but they work best as longer-term solutions. You start on a low dose and titrate upwards over several weeks, so the full therapeutic benefit builds over time. Three months is a realistic timeframe to see meaningful progress (6–12 kg on average), but these medications are designed for sustained weight management beyond 3 months. Always discuss realistic timelines with your prescriber.
How do I find out if I'm eligible without visiting my GP immediately?
Calculate your BMI using our free BMI calculator on this page — it uses NHS guidelines and will show you which category you fall into. This gives you a starting point for discussion. If you have any weight-related health conditions (high blood pressure, type 2 diabetes, sleep apnoea), you're more likely to be eligible. Then book a GP appointment, bring your BMI result, and discuss prescription weight loss options and whether specialist referral 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.