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 You Take Mounjaro With Co-Codamol?
If you're taking Mounjaro (tirzepatide) for weight management and need pain relief, you may wonder whether it's safe to use co-codamol alongside it. This is an important question because some medications can interact with GLP-1 and dual GIP/GLP-1 receptor agonists. The short answer is that you should always discuss this with your GP or prescriber before combining any medicines, 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 Affects Medication Absorption
Mounjaro is a dual GIP and GLP-1 receptor agonist that works by slowing gastric emptying — the speed at which food moves through your stomach. This effect can also influence how quickly other oral medications are absorbed into your bloodstream. Co-codamol (a combination of paracetamol and codeine) is an oral painkiller, which means its absorption could potentially be affected by Mounjaro's action on stomach function.
Codeine is metabolised in the liver and converted to morphine, which is responsible for most of its pain-relief effects. While Mounjaro doesn't directly interact with codeine metabolism, the delayed gastric emptying caused by Mounjaro may slow how quickly co-codamol is absorbed from your stomach. This could mean the pain relief takes longer to work, though the total amount absorbed typically remains unchanged. Your prescriber needs to assess your individual situation, especially if you're taking co-codamol regularly.
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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 GP or Prescriber Needs to Know
Before using co-codamol whilst on Mounjaro, inform your prescriber or GP about:
- How often you take co-codamol (occasional use vs. regular)
- The dose you're taking (8/500mg, 15/500mg, or 30/500mg)
- Any history of stomach or digestion problems
- Other medications you're using
- Any previous adverse reactions to either medicine
Your GP or the prescriber who issued your Mounjaro prescription can give personalised advice based on your health history. They may suggest alternative pain relief options if there's concern about interactions, or reassure you that occasional use is appropriate for your circumstances. Never start or stop any medication without consulting your prescriber first.
- 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.
Will co-codamol work if I'm taking Mounjaro?
Co-codamol should still be effective, but Mounjaro's effect on gastric emptying may delay how quickly it starts working. The total amount absorbed is typically unchanged, but onset may be slower. Always discuss with your GP if pain relief isn't working as expected.
Are there safer pain relief options whilst on Mounjaro?
Paracetamol alone (without codeine) may be a simpler first-line option, as it has fewer potential interactions. Ibuprofen or other NSAIDs can be used but require caution with GLP-1 medications — discuss options with your GP to find the best choice for you.
Can I take co-codamol occasionally with Mounjaro?
Occasional use is likely low-risk for most people, but you must still inform your prescriber. They'll assess your individual health circumstances and advise whether it's appropriate. Never assume occasional use is safe without professional guidance.
Should I take co-codamol at a different time to Mounjaro?
Mounjaro is a once-weekly injection, not a daily oral medicine, so timing of co-codamol doses relative to injection day is unlikely to be a major concern. However, your GP may have specific advice — always ask before adjusting how you take any medication.
What should I do if I experience side effects when combining these medicines?
Stop the co-codamol and contact your GP or call 111 (NHS 24 in Scotland) if you experience unusual symptoms. Nausea, dizziness, or constipation could be from either medicine or an interaction. Seek urgent help (999) for severe symptoms like difficulty breathing or confusion.
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.