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 in Pregnancy: Safety and Alternatives
Mounjaro (tirzepatide) is not recommended during pregnancy and should be stopped if you become pregnant. This guide explains why, how it compares to Wegovy for women of childbearing age, and what your options are if you're planning pregnancy or currently expecting. Both Mounjaro and Wegovy are prescription-only medications requiring a clinical assessment, and pregnancy status is a key part of that assessment with your prescriber.
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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, Wegovy, and Pregnancy: What the Evidence Shows
Mounjaro is contraindicated in pregnancy — meaning it should not be used and must be stopped before conception. The product information states that women of childbearing potential should use effective contraception during treatment and for 4 weeks after the final dose. Animal studies have not shown harm, but there is insufficient human data in pregnancy to establish safety.
Wegovy (semaglutide) has the same contraindication — it is also not recommended in pregnancy and requires the same contraceptive precautions. Both medications are GLP-1 or dual GIP/GLP-1 receptor agonists, and pregnancy safety data for this drug class is limited.
If you are taking either medication and planning to become pregnant, speak to your GP or prescriber immediately. You will need to stop the injection and allow sufficient time to elapse before conception. Your prescriber can discuss safer weight management approaches during pregnancy and postpartum.
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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.
Choosing Between Mounjaro and Wegovy: Pregnancy Planning Considerations
For women who want to plan future pregnancy, both Mounjaro and Wegovy require the same precautions — neither is suitable during pregnancy itself. However, some women may prefer one over the other based on other factors like injection frequency or side effect profile.
Before starting either medication, always disclose if you are planning pregnancy in the next 1–2 years. Your prescriber can help you weigh the benefits of weight loss treatment now against the timing of conception. During pregnancy, the NHS recommends managing weight through safe dietary changes and approved physical activity. Our GLP-1 weight loss calculator can help you understand projected outcomes if you decide to continue treatment before pregnancy planning.
- 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.
Is Mounjaro safe in pregnancy?
No. Mounjaro is contraindicated in pregnancy — it should not be used and must be stopped if you become pregnant. There is insufficient safety data in human pregnancy. If you are pregnant or planning pregnancy, speak to your GP or prescriber immediately.
What's the difference between Mounjaro and Wegovy in pregnancy?
Both have identical contraindications — neither is safe in pregnancy and both require contraception during use. Wegovy is a GLP-1 agonist; Mounjaro is a dual GIP/GLP-1 agonist. For pregnancy planning, the choice between them is based on other factors, not pregnancy safety (both are equally not recommended).
Can I stop Mounjaro and then get pregnant?
Yes. You should stop Mounjaro at least 4 weeks before attempting conception. Your prescriber may recommend a longer gap depending on your individual circumstances. After stopping, your fertility is not affected — the medication clears your system within days to weeks.
What weight management options are safe during pregnancy?
During pregnancy, the NHS recommends a balanced diet, gentle physical activity (if previously active), and regular GP monitoring. gradual weight management is not appropriate. Weight management medications including Mounjaro and Wegovy are not suitable. Your GP can provide personalised guidance.
Should I use contraception while taking Mounjaro?
Yes. Mounjaro requires effective contraception during treatment and for 4 weeks after stopping. This is because pregnancy safety is not established. Discuss contraceptive options with your GP or prescriber — some oral contraceptives may have reduced absorption if taken at the same time as Mounjaro.
Ready to take control of your weight loss journey?
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