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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Got Pregnant on Mounjaro? Your UK Health Guide
If you've discovered you're pregnant while taking Mounjaro (tirzepatide), it's important to stop the medication immediately and contact your GP or midwife. Mounjaro is not approved for use during pregnancy, and it's essential to get medical advice quickly. This guide covers what you need to know about pregnancy on Mounjaro, contraception guidance, and how Mounjaro compares to Wegovy in terms of pregnancy safety. Both are prescription-only weight management injections available in the UK, but both require careful planning if you're considering pregnancy.
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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.
Mounjaro and Pregnancy — What the Evidence Shows
Mounjaro (tirzepatide) is not recommended during pregnancy. Animal studies have raised safety concerns, which is why the medication's prescribing information advises against use in pregnant women. If you become pregnant while taking Mounjaro, you should stop the injection immediately and inform your GP or midwife.
The UK prescribing guidance states that women of childbearing age taking Mounjaro should use reliable contraception for at least 4 weeks after starting treatment AND 4 weeks after each dose increase. This is because the medication may reduce the effectiveness of oral contraceptives. If you're planning to become pregnant, discuss this with your prescriber at least 3 months in advance so you can plan to stop Mounjaro safely and switch to an alternative approach if needed.
Stopping Mounjaro suddenly is safe — there is no withdrawal risk — but you should not stop without discussing it with your healthcare provider, who may suggest alternative weight management support during pregnancy and beyond.
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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
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Mounjaro vs Wegovy — Pregnancy Safety Comparison
Both Mounjaro and Wegovy are prescription-only and neither is approved for use during pregnancy. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whilst Wegovy (semaglutide) is a GLP-1-only injection. Both are licensed in the UK for weight management in adults, and both require reliable contraception if taken by women who could become pregnant.
The key difference is mechanism: Mounjaro's dual action may produce greater average weight loss in clinical trials, but this doesn't change pregnancy safety. Your choice between them should be based on clinical assessment by your prescriber, taking into account your full health history, any weight-related conditions, and your contraception plans. If you're considering pregnancy in the near future (within 6–12 months), discuss this with your GP before starting either medication — they may suggest alternative weight management approaches that don't involve medications.
- 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.
What should I do if I find out I'm pregnant while taking Mounjaro?
Stop Mounjaro immediately and contact your GP or midwife the same day. Tell them you were taking tirzepatide (Mounjaro). Do not take another dose. Your healthcare provider will assess you and offer appropriate pregnancy support and monitoring. There's no emergency risk from stopping, but medical advice is important.
Can I take Mounjaro while trying to conceive?
No. If you're planning to become pregnant, discuss this with your prescriber at least 3 months before stopping. Mounjaro should be stopped, and you'll need a clear period without the medication before conception attempts. Your GP can discuss alternative weight management support during this time.
What contraception should I use with Mounjaro?
Use a reliable non-oral method (like an IUD, implant, or injection) or add a barrier method to oral contraception. Mounjaro may reduce oral pill effectiveness. You must use contraception for 4 weeks after starting Mounjaro AND 4 weeks after each dose increase. Your GP can advise on the best option for you.
Is Wegovy safer than Mounjaro during pregnancy?
No — both Mounjaro and Wegovy are not approved for pregnancy. Neither should be used if you're pregnant or planning to become pregnant soon. Individual suitability depends on your health circumstances. Your GP will assess which medication, if any, is appropriate based on your personal situation.
Can I restart Mounjaro after pregnancy and breastfeeding?
Mounjaro is not recommended during breastfeeding. Once you've stopped breastfeeding and your GP has cleared you medically, you can discuss restarting weight management medication. A new clinical assessment will be needed, as your circumstances will have changed.
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.