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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Co-Codamol and Mounjaro: Safety and Interactions
If you're taking Mounjaro (tirzepatide) for weight management and also use co-codamol for pain relief, it's important to understand how these medications interact. Co-codamol contains paracetamol and codeine, and when combined with Mounjaro, there are specific considerations you should be aware of. This guide explains the interaction, how to use both safely, and when to consult your GP. Always inform your prescriber of all medications you're currently taking before starting or adjusting any treatment.
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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 Co-Codamol and Mounjaro Interact
Co-codamol is a combination pain reliever containing paracetamol and codeine, commonly used for mild to moderate pain in the UK. Mounjaro is a GIP and GLP-1 receptor agonist injection that may slow gastric emptying (how quickly food leaves your stomach), particularly at lower doses during the initial titration phase. This means paracetamol and codeine absorption may be affected when Mounjaro is present.
- Mounjaro slows stomach emptying, which can delay absorption of oral medications including co-codamol
- Codeine is metabolised in the liver; no direct interaction with tirzepatide is documented
- Paracetamol absorption may be delayed but effectiveness is not significantly reduced
- Individual response varies depending on your dose of Mounjaro and frequency of co-codamol use
The interaction is not considered dangerous, but timing and communication with your GP are important for safe use.
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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.
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Safety Guidance and When to Consult Your GP
Before taking co-codamol while on Mounjaro, always inform your prescriber about any regular pain relief medication you use. If you experience persistent stomach pain, nausea beyond what you'd expect from Mounjaro alone, or notice that co-codamol seems less effective, contact your GP immediately. Do not stop either medication without guidance.
- Take co-codamol at a different time from your Mounjaro injection if possible
- Monitor your pain relief effectiveness and report changes to your GP
- Avoid exceeding the recommended dose of co-codamol (maximum 8 tablets per 24 hours for standard strength)
- Contact your healthcare provider if you develop severe abdominal pain, which could indicate a separate issue
- 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 co-codamol with Mounjaro?
Yes, co-codamol and Mounjaro can be used together, but there is a potential interaction. Mounjaro may slow the absorption of co-codamol due to delayed gastric emptying. This doesn't make co-codamol dangerous, but timing matters. Always inform your prescriber about all medications, including over-the-counter pain relief. Your GP can advise on the safest approach for your individual situation.
Will Mounjaro affect how well co-codamol works?
Mounjaro may delay the absorption of co-codamol, meaning it could take longer to feel pain relief or the effect might be slightly reduced. However, the medication will still work — it may just take a bit longer. If you notice co-codamol is significantly less effective than before starting Mounjaro, discuss this with your GP, as dosing or timing adjustments might help.
Should I take co-codamol at a specific time with Mounjaro?
There's no strict timing requirement, but spacing them out may help. For example, take your Mounjaro injection on your scheduled day, then take co-codamol separately when needed for pain relief. This approach may improve absorption. Your GP or pharmacist can provide personalised timing guidance based on your specific situation.
What should I tell my GP or prescriber about co-codamol use?
Inform them about the frequency and dose of co-codamol you use (occasional vs. regular). This helps them assess any potential risks and monitor you appropriately. Include all over-the-counter medications, supplements, and prescription pain relievers. Your prescriber needs a complete medication picture to ensure Mounjaro is safe for you.
Is codeine safer than paracetamol when taking Mounjaro?
Both components of co-codamol can be used with Mounjaro. Paracetamol absorption may be delayed due to slowed gastric emptying, but codeine is metabolised primarily in the liver and doesn't have a documented direct interaction with tirzepatide. Neither is inherently unsafe with Mounjaro — the key is appropriate dosing and communication with your GP.
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