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 GERD — What You Need to Know
If you have gastro-oesophageal reflux disease (GERD) or acid reflux, you may be concerned about taking Mounjaro for weight management. This guide explains how tirzepatide may affect GERD symptoms, what the evidence shows, and how to discuss this with your GP or prescriber before starting treatment. Understanding the connection between GLP-1 and GLP-1/GIP medications and reflux symptoms will help you make an informed decision about whether Mounjaro is suitable for you.
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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.
How Mounjaro May Affect GERD Symptoms
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that works by slowing gastric emptying — the rate at which food leaves your stomach. This mechanism, whilst helping with appetite regulation, can trigger or worsen acid reflux and GERD symptoms in some people. Clinical trials and post-market data show that indigestion and acid reflux are common side effects, affecting up to 1 in 10 users.
The slowing of stomach emptying means food remains in your stomach longer, which can increase pressure and cause acid to reflux into the oesophagus. For those with existing GERD, this may feel like worsening heartburn, regurgitation, or a burning sensation in the chest or throat. However, it's important to note that this effect often reduces over time as your body adjusts to the medication — many users find symptoms improve after the first 4–8 weeks of treatment.
- Indigestion is reported as very common (affecting more than 1 in 10 people)
- Acid reflux (GORD) is reported as common (affecting up to 1 in 10 people)
- These symptoms may be more pronounced at higher doses (10mg, 15mg)
- Taking Mounjaro with smaller, more frequent meals may help reduce reflux risk
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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.
Access and Cost in the UK — NHS vs Private
In the UK, access to Mounjaro depends on your route: NHS specialist services can prescribe tirzepatide through tier 3 weight management clinics, though availability varies significantly by region and waiting lists can be lengthy. Private online prescribing is also available through GPhC-registered pharmacies following a remote clinical assessment with a UK-licensed prescriber — this route does not require NHS referral.
Private Mounjaro typically costs between £129 and £320 per month depending on the dose you're on. A full induction course (weeks 1–20, building from 2.5mg to 15mg) costs approximately £1,500–£2,500. Your prescriber will assess whether Mounjaro is suitable given your GERD history during your consultation. If you have active GERD, they may recommend additional monitoring or suggest alternative weight loss strategies. Always disclose your full medical history, including any reflux medications (such as omeprazole or famotidine) you're taking.
- 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.
Can I take Mounjaro if I have GERD?
Yes, you may be able to take Mounjaro with GERD, but it requires careful assessment. Your prescriber needs to know about your GERD history and current treatment. The medication may temporarily worsen reflux symptoms, but this often improves as your body adjusts. Your GP can help you weigh the benefits against the risks based on your individual situation.
What's the difference between Mounjaro and Wegovy for GERD risk?
Both are GLP-1 agonists that slow gastric emptying and carry GERD risk. Mounjaro is a dual GIP/GLP-1 agonist, while Wegovy is GLP-1 only. Some evidence suggests the GIP component in Mounjaro may have slightly different reflux patterns, but both can trigger acid reflux. Your prescriber can discuss which option is safer for your GERD status.
How long does Mounjaro reflux typically last?
In many cases, indigestion and reflux symptoms from Mounjaro peak during the first 2–4 weeks and gradually improve as your body adapts, typically within 4–8 weeks. However, some users experience ongoing symptoms. Taking smaller meals, avoiding acidic foods, and staying upright after eating can help. Your GP can recommend reflux medication if symptoms persist.
Will my reflux medication interfere with Mounjaro?
No — common GERD medications like omeprazole, pantoprazole, and famotidine do not interact significantly with Mounjaro. However, Mounjaro may slow the absorption of some oral medications, so it's important to inform your prescriber of all medications you're taking. Take any reflux medication at least 30 minutes before your Mounjaro injection.
What should I tell my prescriber about my GERD when applying for Mounjaro?
Disclose the type of GERD you have (occasional vs chronic), whether it's controlled with medication, any previous complications (stricture, Barrett's oesophagus), and all reflux medications you currently take. Be honest about symptom severity. Your prescriber will use this information to decide if Mounjaro is safe for you or if a different weight loss approach might be more suitable.
Ready to take control of your weight loss journey?
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