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
Who Can't Take Mounjaro — Contraindications Guide
Not everyone can take Mounjaro, even if they meet the BMI criteria for weight management. Certain medical conditions, medications, and life circumstances mean prescription cannot be given safely. Understanding these contraindications—and how they compare to Wegovy eligibility—helps you and your GP determine which treatment, if any, is suitable. This guide covers who cannot take Mounjaro in the UK, key health factors that exclude it, and how Wegovy's restrictions differ as an alternative GLP-1 injection.
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.
Absolute Contraindications — Who Cannot Take Mounjaro
Mounjaro (tirzepatide) cannot be prescribed to:
- Under 18 years old — not approved for children or adolescents; weight management in young people requires specialist paediatric assessment
- Pregnant women — tirzepatide may harm fetal development; women of childbearing age should use effective contraception and avoid pregnancy during treatment
- Breastfeeding women — it is unknown if tirzepatide passes into breast milk; breastfeeding should stop before starting treatment
- Allergy to tirzepatide or excipients — any previous serious allergic reaction to the drug or its ingredients means it cannot be used
- Personal or family history of medullary thyroid cancer (MTC) — tirzepatide carries a black triangle warning due to thyroid risk; anyone with MTC or multiple endocrine neoplasia type 2 (MEN2) cannot take it
- Severe gastroparesis — pre-existing stomach paralysis or severe digestion disorders contraindicate use, as GLP-1 agonists slow gastric emptying further
These are absolute contraindications where Mounjaro must not be prescribed under any circumstances.
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.
Relative Contraindications & Medical Caution — Mounjaro vs Wegovy
Some conditions do not absolutely exclude Mounjaro but require careful assessment by your prescriber. These include pancreatitis history, gallbladder disease, type 1 diabetes, or diabetic retinopathy. Both Mounjaro and Wegovy (semaglutide) have similar contraindications because both are GLP-1-pathway medications, though the dual GIP+GLP-1 mechanism of tirzepatide in Mounjaro differs from Wegovy's GLP-1-only action. Your GP or prescriber will review all medications you take—particularly oral contraceptives, which Mounjaro may reduce absorption of—and assess whether the benefits outweigh risks. If Mounjaro is unsuitable, Wegovy may be an alternative, but it too has similar medical restrictions. Use our free GLP-1 weight loss calculator to explore projected outcomes, then discuss suitability with your healthcare provider.
- 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'm trying to get pregnant?
No. Mounjaro should not be used if you are pregnant or planning pregnancy. Women of childbearing age should use effective contraception during treatment. If you wish to become pregnant, inform your prescriber—they will advise when to stop Mounjaro and how long to wait (typically at least 2 months after your last dose) before trying to conceive.
What if I have a history of pancreatitis—can I take Mounjaro?
A history of pancreatitis is a relative contraindication. Your GP will assess the risk carefully. If you have had pancreatitis, you must disclose this before starting Mounjaro, as GLP-1 medications can trigger pancreatitis in susceptible individuals. Your prescriber may advise against it or monitor you closely if benefits justify the risk.
Is Mounjaro safe if I take oral contraceptives?
Mounjaro may reduce how well oral contraceptives are absorbed. If you take the pill, your prescriber will advise you to use a barrier method (condoms) or switch to a non-oral contraceptive for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase to ensure pregnancy prevention.
How does Mounjaro contraindication compare to Wegovy?
Both Mounjaro and Wegovy share similar contraindications—pregnancy, breastfeeding, allergy, MTC history, and severe gastroparesis exclude both. However, Wegovy's single GLP-1 mechanism differs from Mounjaro's dual GIP+GLP-1 action. Your prescriber will assess which is safer for your individual health profile; neither is universally "safer" but suitability varies per person.
Can I take Mounjaro if I have type 2 diabetes?
Yes. Many people taking Mounjaro also have type 2 diabetes, and tirzepatide helps regulate blood sugar. However, if you also take insulin or sulphonylureas, your diabetes medication doses may need adjustment to prevent low blood sugar. Your GP must review all diabetes medications before prescribing Mounjaro and will monitor you closely during treatment.
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.