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
Can Amitriptyline Cause Weight Loss?
Amitriptyline is a tricyclic antidepressant prescribed in the UK for depression, anxiety, and chronic pain conditions. Rather than causing weight loss, amitriptyline typically causes modest weight gain in most patients — usually 1–3 kg over several months of use. However, individual responses vary significantly. If you're concerned about weight changes while taking amitriptyline, speak to your GP. If you're looking for prescription weight management support in the UK, licensed options are available for eligible adults through both NHS and private routes.
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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.
Prescription Weight Management Options in the UK
If you're interested in prescription weight loss medication in the UK, several options are available for eligible adults. The most commonly prescribed are Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist, and Wegovy (semaglutide), a GLP-1 agonist.
To be eligible for prescription weight loss treatment in the UK, you typically need:
- A BMI of 30 kg/m² or above, or
- A BMI of 27–29.9 kg/m² with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or cardiovascular disease)
Clinical trials have shown that these medications can support significant weight loss medication nhs outcomes when used alongside diet and exercise changes. Mounjaro showed average weight loss of around 15–21% of body weight, whilst Wegovy demonstrated approximately 15% average weight loss in clinical trials. Individual results vary considerably. Try our GLP-1 weight loss calculator to see projected weight loss estimates at different doses.
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 Access vs Private Prescription Weight Loss in the UK
NHS access to prescription weight loss medication is through specialist tier 3 weight management services, which requires a GP referral. Availability and waiting times vary significantly across different NHS regions (ICBs), and some areas have substantial waiting lists. Private access is available through GPhC-registered online prescribing services, where you can request an assessment from a UK-licensed prescriber without NHS referral.
Both routes require a clinical assessment to confirm eligibility and suitability. Your GP can advise on NHS options in your area and whether prescription weight loss uk treatment might be appropriate for your circumstances. If you're considering weight loss support, use our free BMI calculator to understand your current BMI category and discuss options with your healthcare provider.
- 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.
Does amitriptyline cause weight loss?
No — amitriptyline typically causes modest weight gain, usually 1–3 kg over several months of treatment. This is one of the most common side effects. However, individual responses vary. Discuss any weight changes with your GP.
What are the UK-licensed prescription weight loss options?
Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide) are all licensed in the UK for weight management. Eligibility is based on BMI and weight-related health conditions. A prescriber will assess suitability for you individually.
How can I access prescription weight loss medication on the NHS?
You need a referral from your GP to a specialist tier 3 weight management service. Availability varies by region. Waiting times can be several months in some areas. Ask your GP about services in your area.
Is private prescription weight loss available in the UK without NHS referral?
Yes — private online prescribing services can issue prescriptions for licensed weight loss medications following a clinical assessment. This is faster than NHS routes but involves a private cost, typically £129–£320 per month depending on dose.
What makes someone eligible for prescription weight loss treatment in the UK?
You need a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnoea. A prescriber will assess your individual eligibility.
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.