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
Free tracker included with every download this week
Weight Loss Medication Online in the UK
Weight loss medication online is available to eligible UK adults through both NHS specialist services and private prescribing. If you're considering prescription weight management, it's important to understand what options exist, who qualifies, and how to access them safely. This guide covers the UK-licensed medications, eligibility criteria, and the difference between NHS and private routes.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Eligibility
Three prescription-only weight management medications are currently licensed in the UK: Mounjaro (tirzepatide), a once-weekly dual GIP and GLP-1 injection; Wegovy (semaglutide), a once-weekly GLP-1 injection; and Saxenda (liraglutide), a daily GLP-1 injection.
To be eligible for prescription weight loss medication in the UK, you typically need a BMI of 30 or above, or a BMI of 27–29.9 if you have weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply due to increased health risks at lower weights.
Clinical trials show these medications may help with weight management alongside diet and exercise. On average, participants lost between 15–21% of their body weight — though individual results vary significantly. All are prescription-only and require a clinical assessment before being prescribed.
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 Getting Started
In the UK, you can access weight loss medication through two routes. NHS access is through specialist tier 3 weight management services, usually following a GP referral. Availability and waiting times vary significantly by region. Private access is available through GPhC-registered online prescribing services, which offer faster access without NHS referral but involve private costs.
Start by discussing with your GP whether prescription weight loss treatment might be appropriate for you. They can assess your BMI, health conditions, and suitability. If pursuing private prescribing, you'll complete an online clinical assessment with a UK-licensed prescriber who will determine if the medication is safe for you. Use our free BMI calculator to check your starting point, and try our GLP-1 weight loss calculator to estimate potential outcomes at different doses.
Next steps: Arrange a GP appointment to discuss your weight management goals and whether you meet the criteria for prescription medication. Be prepared to discuss your weight, height, medical history, and any weight-related health conditions. Your GP can refer you to NHS specialist services if appropriate, or advise whether private prescribing might suit your circumstances.
- 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 buy weight loss medication online without a prescription in the UK?
No. All prescription weight loss medications (Mounjaro, Wegovy, Saxenda) require a prescription issued by a UK-licensed prescriber. Legitimate online services require a clinical assessment before issuing a prescription. Be cautious of services claiming to sell prescription medication without an assessment — they may be operating illegally.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist with a maximum dose of 15 mg weekly. Wegovy (semaglutide) is a GLP-1 receptor agonist with a maximum dose of 2.4 mg weekly. Clinical trials suggest Mounjaro may produce slightly greater average weight loss, though results vary between individuals. Both are once-weekly injections.
How much does weight loss medication cost on the NHS?
Weight loss medications are available on the NHS for eligible adults, but only through specialist weight management services. There is no direct cost to the patient, though availability depends on your region and NHS service funding. Access can involve waiting lists. Speak to your GP about NHS availability in your area.
How long do I need to take weight loss medication?
This varies by individual and medication. Some people use it short-term to establish healthier habits, whilst others continue longer-term. Your prescriber will discuss duration with you based on your response, health goals, and any side effects. Weight loss medication works best alongside sustained dietary and lifestyle changes.
What happens if I stop taking weight loss medication?
If you stop taking the medication, appetite-regulating effects typically diminish over weeks, and hunger and cravings may return to pre-treatment levels. Weight regain is possible if lifestyle changes are not maintained. Any decision to stop medication should be discussed with your prescriber, who can advise on how to manage the transition safely.
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.