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
Stomach Pain With Mounjaro — What You Need to Know
Stomach pain is one of the most common side effects reported by people taking Mounjaro (tirzepatide) in the UK. While it's typically mild and improves over time, understanding what to expect — and how to access Mounjaro safely — is important for anyone considering this prescription weight management injection. Whether you're exploring NHS options through NICE or considering private prescription routes, knowing the cost and access pathways helps you make an informed decision about whether this GLP-1 medication is right for you.
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.
Stomach Pain With Mounjaro: Cost and Access in the UK
Stomach pain is listed as a very common side effect of Mounjaro, affecting more than 1 in 10 people. The pain is typically mild to moderate abdominal discomfort that often improves as your body adjusts to the medication during dose titration. Most people find that nausea and stomach pain settle within the first few weeks of starting treatment or when moving to a new dose.
What typically happens:
- Initial doses (2.5 mg weeks 1–4) often cause more GI discomfort
- Pain usually peaks in the first 24–48 hours after injection
- Symptoms typically improve by day 3–4 as the week progresses
- Eating smaller, lower-fat meals can help reduce stomach discomfort
- Staying hydrated supports symptom management
If stomach pain is severe, persistent, or spreading to your back, contact your GP immediately — these could indicate pancreatitis, a rare but serious condition requiring urgent medical attention. Your prescriber can advise whether continuing treatment is appropriate or if dose adjustment is needed.
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.
Accessing Mounjaro in the UK: NHS vs Private Cost Routes
In the UK, you can access Mounjaro through two routes: NHS specialist services or private online prescription. NICE has approved tirzepatide for NHS use within tier 3 specialist weight management services, but availability varies significantly by region — some ICBs have waiting lists of 12+ months. Private prescription through a GPhC-registered online pharmacy typically costs between £150–£320 per month depending on your dose, with no waiting list. Both routes require a clinical assessment to confirm you're eligible (BMI 30+ or 27+ with weight-related health conditions). Your GP can refer you to NHS services, or you can arrange a private consultation directly with a licensed UK prescriber. Either way, stomach pain side effects should be discussed with your prescriber before starting treatment.
- 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.
How long does stomach pain with Mounjaro usually last?
Most people experience stomach pain for the first few days after each injection, typically improving by day 4–5. Pain usually decreases over time as your body adjusts during dose titration. If stomach pain persists beyond a week or worsens, contact your prescriber.
What's the average cost of Mounjaro on private prescription in the UK?
Private Mounjaro costs approximately £150–£320 per month depending on your dose. Doses start at 2.5 mg and increase gradually, with the maximum dose being 15 mg weekly. Prices vary between GPhC-registered providers. NHS access is free but involves longer waiting times.
Can I get Mounjaro through the NHS if I have stomach pain concerns?
Yes. NHS access is through specialist tier 3 weight management services following GP referral. You can discuss stomach pain concerns with the specialist team before starting. However, NHS availability is limited and regional — waiting lists can be 6–18 months depending on your area.
Is stomach pain with Mounjaro a sign I should stop taking it?
Not necessarily. Mild to moderate stomach pain is expected and usually improves within days. However, if pain is severe, persistent, or accompanied by back pain, vomiting, or fever, contact your GP immediately — these could indicate pancreatitis. Your prescriber will advise whether to continue, pause, or adjust your dose.
How can I reduce stomach pain when starting Mounjaro?
Eat smaller, frequent meals with lower fat content; stay well hydrated; avoid spicy or greasy foods; and take your injection on an evening so you sleep through the worst symptoms. Your prescriber may also suggest anti-nausea medication. Pain typically improves within a few days without intervention.
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.