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
Does Amitriptyline Cause Weight Loss?
Amitriptyline is a tricyclic antidepressant commonly prescribed in the UK for depression, anxiety, and chronic pain. The short answer: amitriptyline typically does not cause weight loss — in fact, it often leads to weight gain as a side effect. If you're concerned about your weight and managing a health condition, it's worth discussing with your GP whether your current medication might be contributing, and what options are available for weight management alongside your treatment plan.
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 Management Options
If you're struggling with weight gain related to medication or other factors, prescription weight loss medications are available in the UK for eligible adults. The NHS and private prescribers offer several options:
- Mounjaro (tirzepatide) — a once-weekly injection that acts as a dual GIP and GLP-1 receptor agonist, showing an average weight loss of around 15–21% of body weight in clinical trials
- Wegovy (semaglutide) — a once-weekly GLP-1 injection, with clinical evidence supporting approximately 14–15% average weight loss
- Saxenda (liraglutide) — a daily GLP-1 injection option
These are all prescription-only medicines requiring a clinical assessment. You may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions. Calculate your personal BMI using our free BMI calculator above to check where you stand 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.
Next Steps: NHS vs Private Route
In the UK, you have two routes to access prescription weight loss medication. NHS access is through specialist tier 3 weight management services — your GP can refer you, though waiting times and availability vary significantly by region. Private access is faster: a UK-licensed prescriber can assess you for medication following an online clinical consultation with a GPhC-registered pharmacy. Either route requires an honest conversation with a healthcare professional about your weight, medical history, and what's realistic for you. Our free GLP-1 weight loss calculator can help you understand potential outcomes, and our progress tracker lets you monitor your journey once you've started 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.
Does amitriptyline always cause weight gain?
Amitriptyline commonly causes weight gain in many patients, but not everyone experiences it to the same degree. Weight gain is listed as a frequent side effect because the medication can increase appetite and affect metabolism. If you've noticed weight changes since starting amitriptyline, discuss this with your GP — they may adjust the dose, suggest timing changes, or explore alternatives.
Can I stop taking amitriptyline to lose weight?
You should never stop amitriptyline without GP guidance, as it requires gradual withdrawal to avoid withdrawal symptoms and worsening of your underlying condition. Instead, speak to your GP about your weight concerns. They can help you weigh the benefits of the medication against side effects and discuss what options might work best for your overall health.
What's the best weight loss medication available in the UK?
There's no single "best" medication — it depends on your individual health profile, BMI, medical history, and lifestyle. Mounjaro and Wegovy are both effective, NHS-licensed options with strong clinical evidence. Your GP or a licensed prescriber will assess which is most suitable for you following a clinical consultation.
How do I know if I'm eligible for prescription weight loss medication in the UK?
You're typically eligible if your BMI is 30 or above, or 27 or above with weight-related conditions like type 2 diabetes or high blood pressure. Use our free BMI calculator to find your BMI, then speak to your GP or a private prescriber about whether weight loss medication is right for you.
Can I use weight loss medication while taking amitriptyline?
Some medications can interact, so it's essential to inform any prescriber about all medications you're currently taking, including amitriptyline. Your GP or a licensed prescriber will review your full medical history and current medications before prescribing anything. They'll ensure it's safe to combine treatments.
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.