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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Cheapest Weight Loss Medication in the UK
If you're looking for affordable weight management medication in the UK, you have several options depending on your eligibility and budget. Three prescription weight loss medications are currently available: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Access varies significantly between NHS weight loss services and private prescribing, with costs ranging from free through the NHS to approximately £129–£320 monthly privately. This guide explains how to find the most cost-effective option for your situation and eligibility.
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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 and Costs
Three prescription medications are licensed for weight management in the UK:
- Mounjaro (tirzepatide) — Once-weekly injection, 2.5mg to 15mg. Clinical trials showed an average weight loss of 15–21% body weight when combined with lifestyle changes. Private costs typically £180–£320 per month depending on dose.
- Wegovy (semaglutide) — Once-weekly injection, 0.25mg to 2.4mg. Average weight loss around 14.9% body weight in trials. Private costs approximately £129–£250 per month.
- Saxenda (liraglutide) — Daily injection, 0.6mg to 3mg. Average weight loss around 5–6% body weight. Private costs typically £100–£180 monthly.
All three medications are prescription-only and require clinical assessment before being prescribed. Eligibility criteria include a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Individual results vary significantly.
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 and How to Find the Cheapest Option
NHS Access (free) — Weight loss medication is available through specialist tier 3 weight management services. You'll need a GP referral and assessment by a specialist team. However, availability varies significantly by region, and waiting lists can be lengthy in many areas. Contact your GP to ask if your local NHS integrated care board (ICB) offers tier 3 services.
Private Access (£100–£320/month) — Available through GPhC-registered online prescribers following a clinical assessment. No NHS referral needed. Prices vary by dose and provider, so it's worth comparing costs across registered services. Use our free GLP-1 weight loss calculator to understand projected outcomes at different dose levels.
Always ensure any prescriber is UK-licensed and registered with the General Pharmaceutical Council (GPhC).
- 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.
Which weight loss medication is cheapest to buy privately in the UK?
Saxenda (liraglutide) is typically the cheapest at around £100–£180 per month, followed by Wegovy at £129–£250, and Mounjaro at £180–£320. Costs vary by provider and dose. However, "cheapest" doesn't always mean best value — Mounjaro and Wegovy have stronger clinical evidence for weight loss in UK trials. Compare both cost and your personal eligibility before deciding.
Can I get weight loss medication free on the NHS?
Yes. If you meet eligibility criteria (BMI ≥30, or 27–29.9 with weight-related health conditions), you can access weight loss medication free through NHS specialist tier 3 weight management services. Ask your GP for a referral. However, availability varies significantly by region, and waiting lists can be months or longer in many areas.
What eligibility criteria do I need for prescription weight loss medication?
You typically need a BMI of 30 or above, or 27–29.9 kg/m² with at least one weight-related health condition (type 2 diabetes, hypertension, dyslipidaemia, sleep apnoea, or cardiovascular disease). Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage due to higher health risk at lower weights. Use our BMI calculator to check your status, then discuss options with your GP.
How much weight will I lose on weight loss medication?
Clinical trials show average weight loss of 5–21% of body weight depending on the medication and dose, alongside a reduced-calorie diet and increased physical activity. However, individual results vary significantly. Some people lose more, others less. Your GP or prescriber can discuss realistic expectations based on your personal health situation.
Is it safer to use the NHS or private weight loss medication services?
Both are safe if accessed appropriately. NHS services follow NICE guidelines and provide ongoing medical supervision. Private services must be through GPhC-registered prescribers and GPhC-registered pharmacies — verify registration before using. Private services may offer faster access but NHS access is free. Either route requires a proper clinical assessment before prescription.
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.