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
Acid Reflux and Mounjaro — What You Need to Know
Acid reflux (gastro-oesophageal reflux disease or GORD) is a common side effect reported by people taking Mounjaro, the weight management injection licensed in the UK. While not everyone experiences it, understanding how Mounjaro may affect your digestive system — and what to do if it happens — is important information before starting treatment. This guide explains the connection, how often it occurs, and practical steps to manage it.
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 May Cause Acid Reflux
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that works by slowing how quickly food leaves your stomach — a process called delayed gastric emptying. This mechanism helps you feel fuller for longer, supporting weight loss. However, this same effect can increase pressure on your stomach and oesophagus, which may trigger acid reflux symptoms in some people.
In clinical trials, acid reflux (indigestion/GORD) was reported as a common side effect, occurring in up to 1 in 10 people taking Mounjaro. The risk may be higher at higher doses (10 mg, 15 mg) compared to lower starting doses (2.5 mg, 5 mg). Individual factors — such as whether you already have a history of reflux — also influence your personal risk. Your prescriber will assess these factors during your clinical assessment before issuing a prescription.
The NHS notes that indigestion and GORD are manageable, and many people find symptoms improve as their body adjusts to the medication over the first few weeks.
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.
Managing Acid Reflux While Taking Mounjaro
If you experience acid reflux on Mounjaro, several practical steps may help. Eat smaller, more frequent meals rather than large portions — this reduces stomach pressure. Avoid trigger foods like spicy dishes, citrus, chocolate, caffeine, and fatty foods. Don't lie down immediately after eating — wait at least 2–3 hours, or sleep with your head elevated. Stay well hydrated throughout the day.
Over-the-counter antacids or alginates (like Gaviscon) may provide short-term relief. If symptoms persist or worsen, contact your GP or prescriber — they may recommend a proton pump inhibitor (PPI) or H2 blocker, prescription-strength medications that reduce stomach acid. Never stop Mounjaro without medical guidance. Your prescriber can advise whether continuing, adjusting your dose, or switching medication is most appropriate.
- 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 acid reflux a serious side effect of Mounjaro?
Acid reflux is classified as a common (but not serious) side effect of Mounjaro. While uncomfortable, it is usually manageable with lifestyle changes and over-the-counter remedies. However, if you experience severe, persistent stomach pain radiating to your back, seek urgent medical attention — this may indicate pancreatitis, a serious condition requiring emergency care.
How long does Mounjaro acid reflux last?
For many people, acid reflux symptoms improve within the first 4–8 weeks as your body adjusts to the medication. However, if symptoms persist beyond this period, speak to your GP or prescriber. They can recommend stronger medications or discuss whether adjusting your Mounjaro dose might help reduce symptoms.
Can I take antacids while on Mounjaro?
Yes, over-the-counter antacids like Gaviscon, Tums, or Rennie can be taken alongside Mounjaro to manage acid reflux. However, if you need regular antacids or prescription-strength acid-suppressing medications, inform your prescriber — they will ensure these are safe with Mounjaro and your other medications.
Should I stop Mounjaro if I get acid reflux?
No — do not stop Mounjaro without medical guidance. Stopping suddenly may affect your weight loss progress and could carry other health implications. Instead, contact your GP or prescriber. They can assess whether lifestyle changes, medication support, or a dose adjustment might help manage reflux whilst continuing treatment.
How does Mounjaro compare to Wegovy for acid reflux risk?
Both Mounjaro and Wegovy can cause acid reflux as they both slow gastric emptying. Mounjaro (a dual GIP/GLP-1 agonist) and Wegovy (a GLP-1 agonist) have similar reflux rates in clinical data. Your prescriber will assess which is most suitable for you based on your individual health history, including any existing reflux concerns.
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.