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
Using Amitriptyline and Mounjaro Together — What You Need to Know
If you're taking amitriptyline (a tricyclic antidepressant) and considering Mounjaro (tirzepatide) for weight management, it's important to understand how these medications interact. Mounjaro may affect how your body absorbs certain oral medications, including amitriptyline. This means your prescriber needs to know about all medications you're taking before starting Mounjaro. Always inform your GP or the prescriber conducting your clinical assessment about amitriptyline use so they can assess whether Mounjaro is safe for you and whether any dose adjustments are needed.
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.
How Mounjaro Affects Medication Absorption in the UK
Mounjaro (tirzepatide) is a once-weekly injection licensed by the MHRA for weight management in UK adults. It works by activating two hormone pathways—GIP and GLP-1—which slows gastric emptying (how quickly food leaves your stomach). This delayed gastric transit can reduce how quickly your body absorbs oral medications taken at the same time, potentially affecting their effectiveness or levels in your bloodstream.
Amitriptyline absorption: Amitriptyline is a tricyclic antidepressant used for depression, nerve pain, and migraines. It's absorbed orally from the stomach and intestines. If Mounjaro slows this absorption, amitriptyline may take longer to reach therapeutic levels, or levels may be lower than expected. This doesn't necessarily mean you can't take both—it means your prescriber needs to monitor you.
- Always disclose amitriptyline use before starting Mounjaro
- Your prescriber may recommend timing your amitriptyline dose differently
- Regular monitoring may be needed to ensure amitriptyline remains effective
- Never stop either medication without medical guidance
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 Prescribing and Your Clinical Assessment
When seeking Mounjaro through an NHS specialist tier 3 weight management service or via private prescription, the prescriber will conduct a full clinical assessment. You must declare all current medications, including amitriptyline, antidepressants, and other oral medicines. This allows them to assess whether Mounjaro is safe for you and whether your amitriptyline dose needs review.
If you're already taking amitriptyline and want to start Mounjaro, discuss this with your GP first—they may refer you to specialist services or recommend a private clinical assessment. The prescriber may suggest spacing out your medication timings or monitoring your mood and pain control more carefully during the first few weeks of Mounjaro treatment to ensure amitriptyline remains effective.
- 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 take amitriptyline with Mounjaro?
Potentially yes, but only under prescriber supervision. Mounjaro may slow how your body absorbs amitriptyline. Always inform your prescriber about amitriptyline use before starting Mounjaro, and they'll assess whether it's safe and whether any adjustments are needed.
Will Mounjaro stop my amitriptyline from working?
Mounjaro may reduce how quickly amitriptyline is absorbed, potentially lowering its effectiveness. This doesn't mean it won't work, but your prescriber may need to monitor you or adjust timing. Don't stop amitriptyline—contact your prescriber if you notice changes in mood or pain control.
What should I tell my prescriber about amitriptyline?
Tell your prescriber the exact dose of amitriptyline you take, how long you've been taking it, and what it's prescribed for (depression, nerve pain, migraines, etc.). This helps them assess risk and decide whether Mounjaro is appropriate for you.
Should I space out amitriptyline and Mounjaro doses?
This depends on your individual situation. Some prescribers recommend spacing out oral medications from Mounjaro injections to reduce absorption issues. Discuss timing with your prescriber—they may suggest taking amitriptyline at a different time of day than your Mounjaro injection.
What if I'm on amitriptyline and want NHS Mounjaro access?
Discuss this with your GP. NHS Mounjaro is accessed through specialist tier 3 weight management services. Your GP can refer you, and the specialist will assess whether Mounjaro is safe alongside amitriptyline and whether any medication adjustments are needed.
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.