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 Reflux — What You Need to Know
Reflux (acid reflux or GERD) is a common side effect reported by people taking Mounjaro (tirzepatide) in the UK. While not everyone experiences it, understanding this potential effect and how to manage it can help you make an informed decision about weight management treatment. This guide explains what reflux is, why Mounjaro may cause it, and what support is available through the NHS and private prescribing routes.
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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.
Why Mounjaro May Cause Reflux and How to Manage It
Acid reflux (GERD) occurs when stomach acid flows back into the oesophagus, causing heartburn, discomfort, or a burning sensation in the chest. Mounjaro can trigger reflux because it slows gastric emptying — the rate at which food leaves your stomach. This slower digestion may increase stomach pressure and acid exposure to the oesophagus, particularly in the first weeks of treatment or during dose increases.
Reflux is listed as a common side effect in Mounjaro's UK product information, meaning it may affect up to 1 in 10 people. However, many users experience no reflux at all, and symptoms often improve as your body adjusts to the medication over several weeks.
- Eating smaller, more frequent meals — large meals increase stomach pressure
- Avoiding trigger foods — spicy, fatty, or acidic foods can worsen reflux
- Staying upright for 2–3 hours after eating — lying down worsens acid reflux
- Antacids or proton pump inhibitors (PPIs) — ask your prescriber if these are suitable for you
If reflux persists despite these changes, contact your GP or the prescriber who issued your Mounjaro prescription — they may adjust your dose or suggest alternative management strategies.
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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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NHS Prescribing and Private Access for Mounjaro in the UK
Access to Mounjaro in the UK varies depending on your route. NHS specialist tier 3 weight management services can prescribe Mounjaro following NICE approval, and your prescriber will monitor for side effects including reflux during your treatment journey. Private online prescribing is also available through UK-licensed prescribers; you'll receive clinical support and advice on managing side effects, though this typically involves a consultation fee.
Whichever route you choose, always inform your prescriber about any existing reflux conditions or heartburn history before starting Mounjaro. If you're already taking medications for reflux (such as omeprazole or ranitidine), your prescriber may need to adjust these. Use our free GLP-1 weight loss calculator to explore projected weight loss outcomes, and discuss realistic expectations and side effect management with your healthcare provider.
- 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 reflux a serious side effect of Mounjaro?
Reflux is common but usually manageable. Most cases are mild to moderate heartburn rather than severe. However, if you experience severe chest pain, difficulty swallowing, or vomiting, seek medical attention immediately. Your GP can assess whether reflux is a sign that Mounjaro isn't suitable for you or if a dose adjustment is needed.
Will reflux go away once I adjust to Mounjaro?
Many people find reflux improves after the first few weeks as their body adjusts. However, some continue to experience it throughout treatment. Simple lifestyle changes—smaller meals, avoiding triggers, staying upright—often help significantly. If reflux persists, your prescriber can suggest additional support.
Can I take antacids or heartburn medicine with Mounjaro?
Many antacids and heartburn medicines are safe to use with Mounjaro, but you should discuss this with your prescriber first. Some medications may interact with Mounjaro or reduce its effectiveness. Your GP or prescriber can recommend suitable options based on your medical history.
Does Mounjaro cause reflux more often than Wegovy?
Reflux is listed as a common side effect for both Mounjaro (tirzepatide) and Wegovy (semaglutide). However, individual experiences vary widely. Some people report more reflux on one medication than the other, whilst others experience none. Your prescriber can discuss which is more suitable for your situation.
What should I do if reflux is severe when taking Mounjaro?
Contact your prescriber or GP immediately if reflux becomes severe or doesn't improve with lifestyle changes. They may adjust your dose, switch you to an alternative medication, or add additional reflux management. Never stop taking Mounjaro without medical guidance, as your prescriber needs to supervise any changes to your treatment.
Ready to take control of your weight loss journey?
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