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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Can You Take Co Codamol With Mounjaro?
Co-codamol is a common over-the-counter painkiller, and Mounjaro is a prescription weight loss injection. If you're taking both, it's important to understand how they may interact. Co-codamol can affect how your stomach empties, and Mounjaro also slows gastric emptying, which means their combined effect needs careful consideration. Always inform your GP or prescriber about all medications and painkillers you're taking before starting tirzepatide (Mounjaro). Your prescriber will assess whether co-codamol is safe to use alongside your weight management treatment.
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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 and Co Codamol Work Together
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that slows how quickly food moves through your stomach — a process called gastric emptying. Co-codamol contains paracetamol and codeine phosphate, both of which can slow stomach function independently. When taken together, this delayed gastric emptying effect may become more pronounced, potentially increasing nausea, constipation, or stomach discomfort — side effects already common with Mounjaro.
Key points:
- Co-codamol may reduce the absorption of oral medications, including pain relief
- Codeine is an opioid, which can worsen constipation — a frequent Mounjaro side effect
- Your stomach function is already altered by Mounjaro's mechanism
- Taking both together requires prescriber awareness and monitoring
Your GP or the prescriber managing your Mounjaro treatment should review all painkillers you use regularly. Alternative pain relief options like paracetamol alone or non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen may be safer choices, though this depends on your individual health profile.
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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 You Should Tell Your Prescriber
Before starting Mounjaro or any UK prescription weight loss treatment, disclose all medications you're taking, including over-the-counter painkillers like co-codamol. Your prescriber needs this information to assess safety and suitability. If you develop severe stomach pain, persistent nausea, or constipation whilst taking Mounjaro and co-codamol together, contact your GP immediately — these could indicate a more serious condition like pancreatitis or bowel obstruction.
For ongoing pain management during weight loss treatment, ask your prescriber about safer alternatives. Many people find that as they lose weight and their overall health improves, pain levels decrease naturally, reducing the need for regular painkillers. Use our free GLP-1 weight loss calculator to understand potential weight loss outcomes, and discuss any concerns about managing pain alongside your treatment plan with your healthcare team.
- 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 co-codamol with Mounjaro?
Co-codamol can be used with Mounjaro, but requires careful consideration. Both slow stomach function, which may increase side effects like constipation and nausea. Always inform your prescriber before starting Mounjaro if you take co-codamol regularly. Your prescriber may suggest alternative pain relief or monitor you more closely for side effects. Never stop prescribed painkillers without advice, but discuss alternatives with your healthcare team.
Will co-codamol affect how Mounjaro works?
Co-codamol is unlikely to reduce Mounjaro's weight loss effectiveness directly. However, delayed gastric emptying from both medications together may affect how quickly other oral medications are absorbed. This is why prescriber awareness is essential. If you're concerned about Mounjaro's effectiveness, use our free BMI calculator to track your progress objectively and discuss results with your prescriber.
What painkillers are safer to use with Mounjaro?
Paracetamol alone (without codeine) is generally considered safer with Mounjaro than co-codamol. Some NSAIDs like ibuprofen may also be suitable, though these carry their own risks if taken long-term. Your GP can recommend the best option based on your health history. Discuss any chronic pain with your prescriber — weight loss itself often reduces pain as stress on joints decreases.
What should I do if I experience severe stomach pain on Mounjaro and co-codamol?
Seek immediate medical attention. Severe stomach pain spreading to the back could indicate pancreatitis, a serious side effect of GLP-1 medications. Do not assume it's just constipation or indigestion. Contact your GP or attend A&E immediately. Always keep your healthcare team informed of all medications and supplements you're taking when reporting symptoms.
Is Mounjaro vs Wegovy different regarding pain relief?
Both Mounjaro and Wegovy slow gastric emptying, so the same cautions apply to co-codamol use with either medication. Mounjaro is a dual GIP+GLP-1 agonist, while Wegovy contains semaglutide (GLP-1 only), but gastric effects are similar. Co-codamol carries the same risks with both. Your prescriber will advise based on which medication is recommended for you and your full medical history.
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.