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
Best Contraceptive Pill Weight Loss in the UK
If you're concerned about weight gain from your contraceptive pill, you're not alone — many people experience this side effect. However, if you have a BMI that falls into the overweight or obese range, prescription weight management options are now available in the UK. This guide explores your options through the NHS and private healthcare, including GLP-1 weight loss medications that may help support sustainable weight loss alongside lifestyle changes. We'll help you understand what's available and how to start a conversation with your GP.
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 Prescription Weight Loss Options Available
For adults managing weight-related health concerns, several prescription medications are now licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist injection administered once weekly. Clinical trials showed participants lost an average of 15–21% of their body weight, though individual results vary significantly.
- Wegovy (semaglutide) — a GLP-1 receptor agonist injection also given once weekly. Evidence suggests average weight loss of around 15% of body weight in clinical trials.
- Saxenda (liraglutide) — a daily GLP-1 injection, an alternative if weekly injections aren't preferred.
You may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions such as high blood pressure, type 2 diabetes, or sleep apnoea. Our free GLP-1 weight loss calculator can help you estimate potential weight loss outcomes at different doses, while our BMI calculator lets you check your current BMI against NHS thresholds.
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: How to Access Weight Management Support
Access to prescription weight loss medication in the UK comes through two routes:
- NHS route: Request a referral from your GP to a tier 3 specialist weight management service. Availability and waiting times vary significantly by region, but this route is free at point of care.
- Private route: Online consultations with UK-licensed prescribers offer faster access without an NHS referral. A clinical assessment determines eligibility, and medication is dispensed by regulated pharmacies.
Before pursuing either route, use our BMI calculator to check where you sit against NHS guidelines. Your GP can advise on NHS options and discuss whether prescription medication is appropriate alongside dietary changes and increased physical activity. Weight loss is most effective when combining medication with lifestyle modifications.
- 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 contraceptive pills cause weight gain?
Some contraceptive pills — particularly older formulations with higher hormone doses — may cause modest weight gain in some people. This varies greatly between individuals. If you're experiencing weight gain, discuss alternative pill types with your GP, and if you have concerns about your BMI, your GP can refer you to weight management services.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro uses a dual GIP and GLP-1 mechanism, while Wegovy uses GLP-1 only. Clinical trials suggest Mounjaro may result in slightly greater average weight loss (15–21% vs 15%), but individual results vary considerably. Both require a prescription and clinical assessment. Our GLP-1 weight loss calculator helps compare projected outcomes.
How do I know if I'm eligible for prescription weight loss medication in the UK?
You may be eligible if your BMI is 30 or above, or 27 or above with weight-related conditions like high blood pressure or type 2 diabetes. Check your BMI using our free BMI calculator, then discuss eligibility with your GP or book a private online consultation with a UK-licensed prescriber.
How long does weight loss medication take to work?
Weight loss typically begins within 2–4 weeks of starting, though results vary. Most people taking Mounjaro or Wegovy see noticeable weight loss over 8–12 weeks. Results are best when combined with reduced-calorie diet and increased physical activity. You can track your progress over time using our free progress tracker.
Can I get weight loss injections on the NHS?
Yes, but NHS access is through specialist tier 3 weight management services by GP referral. Availability varies significantly by region, and waiting lists can be long. Private online consultations offer faster access without referral. Both routes require clinical assessment to confirm suitability.
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.