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 vs Wegovy for Acid Reflux Treatment
Acid reflux is a common side effect reported by people taking weight loss injections like Mounjaro and Wegovy. Both medications work differently, and acid reflux severity varies between individuals. This guide compares how Mounjaro (tirzepatide) and Wegovy (semaglutide) affect acid reflux, what the clinical evidence shows, and how to discuss this with your GP if you're considering either treatment. Remember, both are prescription-only medicines requiring clinical assessment and are used alongside lifestyle changes, not instead of them.
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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 Wegovy Affect Acid Reflux Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) activates only the GLP-1 pathway. This mechanism difference may influence side effects including acid reflux. In the SURMOUNT-1 clinical trial, indigestion and gastro-oesophageal reflux disease (GORD) were reported as common side effects in people taking Mounjaro, occurring in approximately 1 in 10 participants. Wegovy (tested in the STEP trials) similarly reported indigestion and acid reflux as common side effects. The tirzepatide dose escalation schedule—starting at 2.5 mg and increasing weekly—may affect how quickly acid reflux develops. Some people experience reflux symptoms more noticeably at higher doses. Wegovy's slower starting dose (0.25 mg) means a more gradual onset, which may suit some individuals better. Neither medication directly causes acid reflux in the medical sense; rather, both slow gastric emptying (how quickly food leaves the stomach), which can trigger reflux symptoms in susceptible individuals.
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Managing Acid Reflux and Choosing Between Them
If you already have a history of acid reflux or GORD, your prescriber needs to know before starting either medication. Both Mounjaro and Wegovy are suitable for people with existing reflux, but your GP may recommend additional management strategies such as antacids, H2-receptor blockers, or proton pump inhibitors (PPIs). Symptoms often improve as your body adjusts to the medication over several weeks. If reflux persists or worsens, your prescriber may adjust your dose, pause treatment, or switch to the alternative. Use our free BMI calculator to check your eligibility first, then discuss acid reflux concerns directly with your prescriber during your clinical assessment. Individual responses vary—some people experience no reflux at all, while others find symptoms resolve naturally as treatment continues.
- 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.
Does Mounjaro cause acid reflux more than Wegovy?
Clinical trials show both medications report acid reflux as a common side effect at similar rates. Mounjaro's dual mechanism may theoretically differ, but real-world data doesn't show clear superiority for either. Individual response varies significantly. Your prescriber can help assess which suits you based on your personal reflux history and other health factors.
Can I take acid reflux medication with Mounjaro or Wegovy?
Yes. Antacids, H2-blockers, and proton pump inhibitors (PPIs) are commonly used alongside both medications. Inform your prescriber of any reflux medications you take, as there are minimal known interactions with either GLP-1 or tirzepatide. Your GP can advise on the best reflux management approach for you specifically.
How long does acid reflux last when starting weight loss injections?
Reflux symptoms often improve within 2–4 weeks as your body adjusts. Some people experience symptoms only during the dose titration phase and find relief once stabilised at their maintenance dose. If reflux persists beyond 4–6 weeks, contact your prescriber to discuss whether dose adjustment or alternative management is needed.
Which is better for acid reflux, Mounjaro or Wegovy?
Neither is definitively "better" for acid reflux. Both cause similar rates of reflux side effects in clinical trials. The choice depends on your individual health profile, other side effects, prescriber recommendation, and personal tolerance. A clinical assessment will determine which is most suitable for you.
Is acid reflux a reason not to take Mounjaro or Wegovy?
No. Existing acid reflux is not a contraindication for either medication. Many people with GORD successfully use these injections alongside reflux medications. Tell your prescriber about your reflux history during assessment so they can monitor you and adjust treatment if needed.
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