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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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 (tirzepatide) in the UK. This NHS-aligned guide explains why this happens, what to expect, and how to manage symptoms safely. If you're considering Mounjaro as a prescription weight management option, understanding potential side effects is essential.
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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 Does Mounjaro Cause Acid Reflux?
Mounjaro works by slowing gastric emptying—how quickly food leaves your stomach. This mechanism, which supports the main effect of reducing appetite, can increase stomach acid exposure to the oesophagus, triggering reflux symptoms. Acid reflux is listed as a "common" side effect in Mounjaro prescribing information, meaning it may affect up to 1 in 10 people taking the medication.
- Slowed stomach emptying increases the time acid spends near the oesophagus
- Mounjaro's dual GIP and GLP-1 mechanism affects gastric motility
- Individual risk varies—some people experience reflux, others do not
- Symptoms often improve over time as the body adjusts to the tirzepatide dose
Compare this to other weight loss medications: Wegovy (semaglutide) also causes reflux in some users, though clinical trial data shows similar prevalence. Our GLP-1 weight loss calculator can help you understand potential side effect patterns at different doses.
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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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Managing Acid Reflux While on Mounjaro
If you develop reflux symptoms while taking Mounjaro, several evidence-based strategies can help. Always inform your prescriber or GP if symptoms are severe or persistent—they may adjust your dose, suggest over-the-counter antacids, or recommend lifestyle changes. NHS guidance suggests eating smaller, more frequent meals, avoiding trigger foods (spicy, fatty, acidic), and waiting 2–3 hours after eating before lying down.
- Take Mounjaro as prescribed—do not skip doses to avoid reflux
- Discuss over-the-counter options with your GP (antacids, H2 blockers, proton pump inhibitors)
- Stay upright after meals when possible
- Monitor symptoms with our free progress tracker to identify patterns and share with your prescriber
- 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 from Mounjaro is usually mild to moderate and manageable with lifestyle changes or over-the-counter treatments. However, if you experience severe, persistent reflux, chest pain, or difficulty swallowing, contact your GP immediately, as these could indicate more serious conditions requiring investigation.
Will acid reflux go away while on Mounjaro?
For many people, reflux improves as the body adjusts to the medication—often within weeks. However, some individuals experience ongoing symptoms. Your prescriber may suggest dose adjustments, dietary changes, or medication to manage reflux while continuing Mounjaro treatment.
Can I take antacids while on Mounjaro?
Yes, most over-the-counter antacids are safe to use alongside Mounjaro. However, some medications can affect how Mounjaro is absorbed. Always inform your prescriber of any medications you're taking, and discuss which antacids are suitable for you specifically.
How does Mounjaro's reflux risk compare to Wegovy?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) cause acid reflux in some users, as both slow gastric emptying. Clinical trial data shows similar reflux prevalence between the two. Your prescriber can discuss which medication suits your individual health profile.
Should I stop Mounjaro if I get acid reflux?
Do not stop Mounjaro without discussing this with your prescriber. Sudden discontinuation isn't recommended. Instead, contact your GP or prescriber—they can explore management strategies, adjust your dose, or discuss alternatives if reflux is significantly affecting your quality of life.
Ready to take control of your weight loss journey?
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