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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Mounjaro and Amitriptyline — Can You Take Them Together?
Mounjaro (tirzepatide) and amitriptyline can potentially be taken together, but this combination requires careful monitoring by your GP or prescriber. Amitriptyline is a tricyclic antidepressant commonly used for depression, anxiety, and chronic pain in the UK. If you're taking both medications, your prescriber needs to assess the interaction risk and monitor you closely. Always inform your prescriber of all medications you're taking before starting Mounjaro, as individual health circumstances vary significantly.
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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.
How Mounjaro and Amitriptyline May Interact
Mounjaro works as a dual GIP and GLP-1 receptor agonist, slowing how quickly food leaves your stomach and helping regulate appetite. Amitriptyline is a tricyclic antidepressant that affects neurotransmitters in the brain and can also slow gastric emptying—the speed at which food moves through your digestive system.
When both medications slow gastric emptying, there's a potential for combined digestive effects, which may increase the risk of stomach discomfort, nausea, or constipation. Additionally, amitriptyline can cause drowsiness and dizziness, and Mounjaro may cause fatigue—taking both together could amplify these effects. Your prescriber will weigh these risks against the benefits of treatment for your individual health needs.
This is why disclosure is essential: always tell your GP or prescriber that you take amitriptyline before starting Mounjaro, or mention Mounjaro if you're already on amitriptyline and your dosing is being adjusted.
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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.
What Your Prescriber Will Consider
Your prescriber will assess whether the benefits of Mounjaro for weight management outweigh the interaction risks with amitriptyline. They may suggest starting Mounjaro at the lowest dose (2.5 mg once weekly) and monitoring you closely during the first few weeks. You may be asked to report any new or worsening digestive symptoms, unusual drowsiness, or changes in mood.
In some cases, your GP might recommend adjusting amitriptyline dosing if side effects become problematic—never adjust either medication yourself. Regular check-ins with your healthcare team are important. If you experience severe stomach pain, persistent vomiting, or significant changes in how you feel, contact your GP immediately. Use our free BMI calculator and GLP-1 weight loss calculator to track your baseline health metrics and potential progress.
- 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.
Is it safe to take Mounjaro with amitriptyline?
Mounjaro and amitriptyline can potentially be taken together, but the combination requires clinical assessment and monitoring. Both slow gastric emptying, which may increase digestive side effects. Your prescriber will evaluate your individual health circumstances and decide if the benefits outweigh the risks. Never start either medication without informing your prescriber of all other medications.
What side effects might increase when taking both medications?
Potential combined effects include nausea, constipation, stomach discomfort, drowsiness, and fatigue. These are not assured to occur, but the risk is higher when both medications affect digestion and the nervous system. Close monitoring during the first few weeks helps catch any problems early. Report new or worsening symptoms to your GP.
Should I stop amitriptyline if I start Mounjaro?
No—never stop or adjust amitriptyline without your GP's guidance. Stopping amitriptyline abruptly can cause withdrawal effects and mood changes. If you're considering Mounjaro and currently take amitriptyline, discuss this with your prescriber. They may adjust doses or timing to minimise interactions, but both medications can often be continued safely with proper monitoring.
How will my GP monitor me if I take both medications?
Your prescriber will typically recommend regular check-ins—initially every 2–4 weeks when starting Mounjaro. They'll ask about digestive symptoms, mood, energy levels, and any new side effects. You may be asked to report symptoms between appointments if anything concerns you. Be honest about all effects, even mild ones, to help your GP optimise your treatment plan.
Does amitriptyline affect how well Mounjaro works?
Amitriptyline is unlikely to reduce Mounjaro's weight loss effectiveness directly. However, if amitriptyline causes drowsiness or fatigue, it might reduce your motivation for physical activity, which supports weight loss. Mounjaro's effectiveness also depends on diet and exercise. Your prescriber will consider your full health picture, including depression or pain management, when assessing treatment success.
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.