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
Can You Take Omeprazole With Mounjaro?
Yes, omeprazole and Mounjaro can generally be taken together, but you must inform your prescriber about all medications you're using. Mounjaro (tirzepatide) is a prescription-only GLP-1 and GIP receptor agonist injection licensed in the UK for weight management. Because Mounjaro affects how your stomach works and how oral medications are absorbed, it's essential your GP or prescriber knows about any acid reflux treatments or other medicines you take. This guide covers UK-specific information about combining these medications safely.
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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 Affects Medication Absorption
Mounjaro slows gastric emptying — the rate at which food leaves your stomach — which can affect how quickly oral medications, including omeprazole, are absorbed. While omeprazole is unlikely to be directly unsafe with Mounjaro, the timing and effectiveness of your stomach medication may be altered. Always tell your prescriber about omeprazole or any other acid reflux treatment before starting Mounjaro, including proton pump inhibitors (PPIs) like omeprazole, lansoprazole, or pantoprazole. Your GP may advise spacing doses apart or monitoring symptoms more closely. If you experience increased heartburn or indigestion after starting Mounjaro — which is a common side effect — your prescriber may recommend adjusting your omeprazole dose or switching to an alternative.
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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.
What to Tell Your Prescriber About Medications
When seeking a Mounjaro prescription through the NHS or a private prescriber, provide a full list of all medications including omeprazole, other acid reflux treatments, diabetes medicines, contraceptives, and any over-the-counter medicines. This allows your prescriber to assess your individual safety profile and make informed decisions about dosing and monitoring. If you're accessing Mounjaro through an online prescriber following a clinical assessment, ensure the assessment form captures your full medication history. Never stop omeprazole without medical advice, even if starting Mounjaro, as acid reflux control is important for your health.
- 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.
Will omeprazole stop working if I take Mounjaro?
Mounjaro may slightly slow how quickly omeprazole is absorbed due to slower stomach emptying, but omeprazole is unlikely to stop working entirely. Your prescriber can monitor your symptoms and adjust doses if needed. Always inform them before starting Mounjaro.
Can Mounjaro cause acid reflux or indigestion?
Yes — indigestion is a common side effect of Mounjaro, affecting up to 1 in 10 people in clinical trials. If you already take omeprazole for acid reflux, Mounjaro may temporarily worsen symptoms. Your GP can review your acid reflux treatment and adjust it if necessary.
Should I space omeprazole and Mounjaro injections apart?
Omeprazole is a daily oral tablet and Mounjaro is a once-weekly injection, so timing them apart isn't typically necessary. However, discuss the exact timing of your omeprazole dose with your prescriber — they may recommend taking it at a consistent time each day for best results.
Is it safe to start Mounjaro if I take omeprazole?
Yes, it is generally safe to take both together, but your prescriber must know about your omeprazole use during clinical assessment. They will check for any contraindications and monitor you. Never start Mounjaro without disclosing all current medications to your prescriber.
What if my indigestion gets worse on Mounjaro?
Contact your GP if indigestion worsens significantly after starting Mounjaro. Your prescriber may increase your omeprazole dose, switch to a different acid reflux treatment, or adjust your Mounjaro dose. Some indigestion typically improves as your body adjusts to Mounjaro over weeks.
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.