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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Perimenopause Weight Loss — UK Prescription Options
Weight gain during perimenopause is common due to hormonal changes, but prescription weight loss medication is now available in the UK for eligible adults. If you're struggling with weight management during this transition, your GP can assess whether prescription options like Mounjaro or Wegovy might support your weight loss efforts alongside lifestyle changes. This guide explains what's available through both NHS and private routes 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 Prescription Weight Loss Options
Three main prescription weight loss medications are licensed in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All work by affecting hormones that control appetite and blood sugar. Mounjaro and Wegovy are particularly popular for weight management UK as they're once-weekly injections. Clinical trials show average weight loss of 15–21% with Mounjaro and approximately 15% with Wegovy over 12–18 months, though individual results vary significantly.
- Mounjaro: Once-weekly injection, doses 2.5–15 mg, dual GIP/GLP-1 mechanism
- Wegovy: Once-weekly injection, doses 0.25–2.4 mg, GLP-1 mechanism
- Saxenda: Daily injection, doses 0.6–3 mg, GLP-1 mechanism
You're eligible for prescription weight loss if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or hypertension. For South Asian or Black African heritage adults, lower thresholds apply. These medications work alongside diet and activity changes, not instead of them.
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 in the UK
NHS access: Through specialist tier 3 weight management services via GP referral. Availability varies by region and waiting times can be lengthy. Private access: Through GPhC-registered online pharmacies following clinical assessment—faster access but at cost (approximately £129–£320 monthly depending on dose). Your GP can advise on NHS availability in your area and may support you exploring private options. Either route requires a prescriber assessment to confirm suitability.
- Start by discussing weight loss medication NHS options with your GP
- Ask about specialist weight management services in your local integrated care board
- Private prescribing is available without NHS referral if you wish to explore this route
- Track your weight loss progress with our free progress tracker once you start treatment
- 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 get weight loss medication on the NHS during perimenopause?
Yes, if you meet eligibility criteria (BMI ≥30 or ≥27 with weight-related health conditions), you can be referred to NHS specialist weight management services by your GP. However, availability and waiting times vary significantly across UK regions. Ask your GP about services in your area.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials show average weight loss of 15–21% with Mounjaro and approximately 15% with Wegovy over 12–18 months. Individual results vary considerably based on dose, diet, activity, and personal factors. Results are not assured.
Are there side effects I should know about?
Common side effects include nausea, diarrhoea, and stomach discomfort—usually temporary. Serious side effects are rare but include pancreatitis symptoms (severe stomach pain). Your prescriber will discuss all risks and benefits with you before starting.
Can I use our BMI calculator to check my eligibility?
Yes. Use our free BMI calculator to find your current BMI. If it's 30 or above, or 27–29.9 with weight-related health conditions, you may be eligible. Always discuss results with your GP for personalised advice.
How is perimenopause weight different from other weight gain?
Perimenopause weight gain is often due to hormonal shifts (declining oestrogen), slower metabolism, and changes in fat distribution. Prescription GLP-1 weight loss medication may help, but it works best with dietary and lifestyle support tailored to this life stage.
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.